CSAT 2016: every question, solved
80 questions from the official UPSC Prelims 2016 paper, in paper order. Tap an option; the answer and the reason appear instantly.
Read the passage
Accountability, or the lack of it, in governance generally, and civil services, in particular, is a major factor underlying the deficiencies in governance and public administration. Designing an effective framework for accountability has been a key element of the reform agenda. A fundamental issue is whether civil services should be accountable to the political executive of the day or to society at large. In other words, how should internal and external accountability be reconciled ? Internal accountability is sought to be achieved by internal performance monitoring, official supervision by bodies like the Central Vigilance Commission and Comptroller and Auditor General, and judicial review of executive decisions. Articles 311 and 312 of the Indian Constitution provide job security and safeguards to the civil services, especially the All India Services. The framers of the Constitution had envisaged that provision of these safeguards would result in a civil service that is not totally subservient to the political executive but will have the strength to function in larger public interest. The need to balance internal and external accountability is thus built into the Constitution. The issue is where to draw the line. Over the years, the emphasis seems to have tilted in favour of greater internal accountability of the civil services to the political leaders of the day who in turn are expected to be externally accountable to the society at large through the election process. This system for seeking accountability to society has not worked out, and has led to several adverse consequences for governance.
Some special measures can be considered for improving accountability in civil services. Provisions of articles 311 and 312 should be reviewed and laws and regulations framed to ensure external accountability of civil services. The proposed Civil Services Bill seeks to address some of these requirements. The respective roles of professional civil services and the political executive should be defined so that professional managerial functions and management of civil services are depoliticized. For this purpose, effective statutory civil service boards should be created at the centre and in the states. Decentralization and devolution of authority to bring government and decision making closer to the people also helps to enhance accountability.
According to the passage, which of the following factor/factors led to the adverse consequences for governance/public administration ?
- 1. Inability of civil services to strike a balance between internal and external accountabilities
- 2. Lack of sufficient professional training to the officers of All India Services
- 3. Lack of proper service benefits in civil services
- 4. Lack of Constitutional provisions to define the respective roles of professional civil services vis-a-vis political executive in this context
Select the correct answer using the code given below :
Answer (c) & explanation
The answer is 1 and 4 only (c). Step 1: the passage says the tilt towards internal accountability to political leaders "has led to several adverse consequences". That is the failure to balance internal and external accountability, so statement 1 is right. Step 2: it also says the roles of civil servants and the political executive should be defined, which means they are not clearly defined now. So statement 4 is right. Step 3: training of officers (2) and service benefits (3) are never mentioned. So options (a), (b) and (d) fail.
Tip: in "according to the passage" questions, tick a statement only if you can point to a line that supports it. Sensible ideas from outside the passage do not count.
Answer as per the official UPSC answer key.
Read the passage
Accountability, or the lack of it, in governance generally, and civil services, in particular, is a major factor underlying the deficiencies in governance and public administration. Designing an effective framework for accountability has been a key element of the reform agenda. A fundamental issue is whether civil services should be accountable to the political executive of the day or to society at large. In other words, how should internal and external accountability be reconciled ? Internal accountability is sought to be achieved by internal performance monitoring, official supervision by bodies like the Central Vigilance Commission and Comptroller and Auditor General, and judicial review of executive decisions. Articles 311 and 312 of the Indian Constitution provide job security and safeguards to the civil services, especially the All India Services. The framers of the Constitution had envisaged that provision of these safeguards would result in a civil service that is not totally subservient to the political executive but will have the strength to function in larger public interest. The need to balance internal and external accountability is thus built into the Constitution. The issue is where to draw the line. Over the years, the emphasis seems to have tilted in favour of greater internal accountability of the civil services to the political leaders of the day who in turn are expected to be externally accountable to the society at large through the election process. This system for seeking accountability to society has not worked out, and has led to several adverse consequences for governance.
Some special measures can be considered for improving accountability in civil services. Provisions of articles 311 and 312 should be reviewed and laws and regulations framed to ensure external accountability of civil services. The proposed Civil Services Bill seeks to address some of these requirements. The respective roles of professional civil services and the political executive should be defined so that professional managerial functions and management of civil services are depoliticized. For this purpose, effective statutory civil service boards should be created at the centre and in the states. Decentralization and devolution of authority to bring government and decision making closer to the people also helps to enhance accountability.
With reference to the passage, the following assumptions have been made :
- 1. Political executive is an obstacle to the accountability of the civil services to the society
- 2. In the present framework of Indian polity, the political executive is no longer accountable to the society
Which of these assumptions is/are valid ?
Answer (a) & explanation
Only assumption 1 is valid (a). Step 1: the passage says routing accountability through political leaders "has not worked out", and calls for depoliticising the civil services. So the author treats the political executive as a block between civil servants and society. Assumption 1 holds. Step 2: the passage also says politicians are accountable to society "through the election process". So assumption 2, that they are no longer accountable, goes against the passage. Step 3: so options (b), (c) and (d) fail.
Tip: an assumption must fit what the author already believes. If the passage says the opposite of a statement, as here with elections, reject that statement at once.
Answer as per the official UPSC answer key.
Read the passage
Accountability, or the lack of it, in governance generally, and civil services, in particular, is a major factor underlying the deficiencies in governance and public administration. Designing an effective framework for accountability has been a key element of the reform agenda. A fundamental issue is whether civil services should be accountable to the political executive of the day or to society at large. In other words, how should internal and external accountability be reconciled ? Internal accountability is sought to be achieved by internal performance monitoring, official supervision by bodies like the Central Vigilance Commission and Comptroller and Auditor General, and judicial review of executive decisions. Articles 311 and 312 of the Indian Constitution provide job security and safeguards to the civil services, especially the All India Services. The framers of the Constitution had envisaged that provision of these safeguards would result in a civil service that is not totally subservient to the political executive but will have the strength to function in larger public interest. The need to balance internal and external accountability is thus built into the Constitution. The issue is where to draw the line. Over the years, the emphasis seems to have tilted in favour of greater internal accountability of the civil services to the political leaders of the day who in turn are expected to be externally accountable to the society at large through the election process. This system for seeking accountability to society has not worked out, and has led to several adverse consequences for governance.
Some special measures can be considered for improving accountability in civil services. Provisions of articles 311 and 312 should be reviewed and laws and regulations framed to ensure external accountability of civil services. The proposed Civil Services Bill seeks to address some of these requirements. The respective roles of professional civil services and the political executive should be defined so that professional managerial functions and management of civil services are depoliticized. For this purpose, effective statutory civil service boards should be created at the centre and in the states. Decentralization and devolution of authority to bring government and decision making closer to the people also helps to enhance accountability.
Which one of the following is the essential message implied by this passage ?
Answer (d) & explanation
The essential message is the need for reforms in civil service accountability (d). Step 1: the passage first explains the problem, then lists special measures: reviewing Articles 311 and 312, a Civil Services Bill and independent boards. A list of fixes means the message is reform. Step 2: option (a) is too absolute. Civil servants are accountable, only the balance is off. Step 3: option (b), about educated people avoiding politics, is not discussed. Option (c) is wrong because the framers did build in a balance through Articles 311 and 312.
Tip: the "essential message" usually sits where the author moves from the problem to the solution. Watch for words like "needs" or "measures".
Answer as per the official UPSC answer key.
Read the passage
Accountability, or the lack of it, in governance generally, and civil services, in particular, is a major factor underlying the deficiencies in governance and public administration. Designing an effective framework for accountability has been a key element of the reform agenda. A fundamental issue is whether civil services should be accountable to the political executive of the day or to society at large. In other words, how should internal and external accountability be reconciled ? Internal accountability is sought to be achieved by internal performance monitoring, official supervision by bodies like the Central Vigilance Commission and Comptroller and Auditor General, and judicial review of executive decisions. Articles 311 and 312 of the Indian Constitution provide job security and safeguards to the civil services, especially the All India Services. The framers of the Constitution had envisaged that provision of these safeguards would result in a civil service that is not totally subservient to the political executive but will have the strength to function in larger public interest. The need to balance internal and external accountability is thus built into the Constitution. The issue is where to draw the line. Over the years, the emphasis seems to have tilted in favour of greater internal accountability of the civil services to the political leaders of the day who in turn are expected to be externally accountable to the society at large through the election process. This system for seeking accountability to society has not worked out, and has led to several adverse consequences for governance.
Some special measures can be considered for improving accountability in civil services. Provisions of articles 311 and 312 should be reviewed and laws and regulations framed to ensure external accountability of civil services. The proposed Civil Services Bill seeks to address some of these requirements. The respective roles of professional civil services and the political executive should be defined so that professional managerial functions and management of civil services are depoliticized. For this purpose, effective statutory civil service boards should be created at the centre and in the states. Decentralization and devolution of authority to bring government and decision making closer to the people also helps to enhance accountability.
According to the passage, which one of the following is not a means of enhancing internal accountability of civil services ?
Answer (d) & explanation
People's participation is not a means of internal accountability (d). Step 1: the passage lists the internal means: internal performance monitoring, supervision by bodies like the CVC and CAG, judicial review of executive decisions, and the job safeguards in Articles 311 and 312. Step 2: so options (a), (b) and (c) all appear in the passage as internal means. Step 3: involving people in decisions brings government "closer to the people". That is accountability to society, which is external accountability. So (d) is the odd one out.
Tip: for a "which is NOT" question, tick off every option the passage supports. The one left over is the answer. Read the question word "not" twice.
Answer as per the official UPSC answer key.
Read the passage
In general, religious traditions stress our duty to god, or to some universal ethical principle. Our duties to one another derive from these. The religious concept of rights is primarily derived from our relationship to this divinity or principle and the implication it has on our other relationships. This correspondence between rights and duties is critical to any further understanding of justice. But, for justice to be practiced; virtue, rights and duties cannot remain formal abstractions. They must be grounded in a community (common unity) bound together by a sense of common union (communion). Even as a personal virtue, this solidarity is essential to the practice and understanding of justice.
With reference to the passage, the following assumptions have been made :
- 1. Human relationships are derived from their religious traditions
- 2. Human beings can be duty bound only if they believe in god
- 3. Religious traditions are essential to practice and understand justice
Which of these assumption(s) is/are valid ?
Answer (a) & explanation
Only assumption 1 is valid (a). Step 1: the passage says "our duties to one another derive from these" religious traditions. So human relationships are drawn from religious traditions, and assumption 1 holds. Step 2: assumption 2 says duty is possible only through belief in god. But the passage allows duty to "some universal ethical principle" too. The word only makes 2 wrong. Step 3: assumption 3 says religion is essential to justice. The passage calls the balance of rights and duties, and solidarity, essential, not religion. So options (b), (c) and (d) fail.
Tip: words like only, always and essential often turn a statement false. Check whether the passage really goes that far.
Answer as per the official UPSC answer key.
Read the passage
In general, religious traditions stress our duty to god, or to some universal ethical principle. Our duties to one another derive from these. The religious concept of rights is primarily derived from our relationship to this divinity or principle and the implication it has on our other relationships. This correspondence between rights and duties is critical to any further understanding of justice. But, for justice to be practiced; virtue, rights and duties cannot remain formal abstractions. They must be grounded in a community (common unity) bound together by a sense of common union (communion). Even as a personal virtue, this solidarity is essential to the practice and understanding of justice.
Which one of the following is the crux of this passage ?
Answer (c) & explanation
The crux is that a balance between rights and duties is crucial to justice (c). Step 1: the key line is: "This correspondence between rights and duties is critical to any further understanding of justice." The whole passage builds towards this point. Step 2: option (a), that duties come from religious traditions, is an opening detail, not the main point. Option (d), that rights come from our relationship to god, is also a detail. Step 3: option (b), calling a relationship to the divine a great virtue, is a value judgement the passage never makes.
Tip: the crux is the idea the other sentences support. Supporting details from the start of a passage are common trap options.
Answer as per the official UPSC answer key.
A ate grapes and pineapple; B ate grapes and oranges; C ate oranges, pineapple and apple; D ate grapes, apple and pineapple. After taking fruits, B and C fell sick. In the light of the above facts, it can be said that the cause of sickness was :
Answer (d) & explanation
The cause of sickness was oranges (d). Step 1: B and C fell sick. A and D stayed well. Look for a fruit that both sick people ate and neither healthy person ate. Step 2: B ate grapes and oranges. C ate oranges, pineapple and apple. The fruit common to B and C is oranges. Step 3: check the healthy pair. A ate grapes and pineapple, and D ate grapes, apple and pineapple. Neither ate oranges. Apple (a) and pineapple (b) were eaten by A or D, who stayed well. Grapes (c) were eaten by both A and D.
Tip: in "find the cause" puzzles, the cause appears in every bad case and in none of the good ones. Remove anything a healthy person also had.
Answer as per the official UPSC answer key.
Consider the following statements :
- 1. The rate of population growth is increasing in the country
- 2. The death rate is declining faster in the country compared to birth rate
- 3. The birth rate is declining faster in the country compared to death rate
- 4. Rural-urban migration is taking place regularly in the country
Which one of the following conclusions may be true in the light of the above facts ?
Answer (d) & explanation
Population growth rises because the death rate falls faster than the birth rate (d). Step 1: growth = birth rate − death rate. If the death rate falls faster than the birth rate, the gap between them widens. So growth rises. This matches statements 1 and 2. Step 2: option (a) blames migration. But people moving from villages to cities stay in the same country, so the national total does not change. Step 3: options (b) and (c) use the word only. The facts show both rates falling, so neither single cause explains it. Statement 3 contradicts statement 2, so it cannot be used.
Tip: population growth is simply births minus deaths, plus or minus migration across the border. Internal migration never changes the national count.
Answer as per the official UPSC answer key.
A person X was driving in a place where all roads ran either north-south or east-west, forming a grid. Roads are at a distance of 1 km from each other in a parallel. He started at the intersection of two roads, drove 3 km north, 3 km west and 4 km south. Which further route could bring him back to his starting point, if the same route is not repeated ?
Answer (b) & explanation
He should go 3 km east, then 1 km north (b). Step 1: he goes 3 km north and then 4 km south. So he ends 1 km south of the start. He also went 3 km west. Step 2: to get back, he must go 3 km east and 1 km north. Step 3: check the "no repeat" rule. Going east along the road 1 km south of the start is a new road, then 1 km north brings him home. Option (a) takes him further south. Option (c) takes him further west. Option (d) leaves him 3 km south of where he started.
Tip: in direction problems, add up north–south and east–west moves separately. The net gap in each direction tells you the way home.
Answer as per the official UPSC answer key.
Consider the following statement :
"We shall go either for a picnic or for trekking".
Which of the following, if true, would falsify this claim ?
Answer (d) & explanation
Only "we go for neither" falsifies the claim (d). Step 1: "We shall go either for a picnic or for trekking" means at least one of the two will happen. Step 2: such a claim is broken only when neither happens. So option (d) falsifies it. Step 3: test the others. Option (a), picnic but no trekking, fits the claim. Option (c), trekking but no picnic, also fits. Option (b), about health authorities, has nothing to do with whether the claim is true.
Tip: "either A or B" is false only when both are missing. "If A then B" is false only when A happens and B does not. Learn these two rules; they settle many logic questions.
Answer as per the official UPSC answer key.
There were 50 faculty members comprising 30 males and the rest females. No male faculty member knew music, but many of the female faculty members did. The Head of the institution invited six faculty members to a tea party by draw of lots. At the party it was discovered that no member knew music. The conclusion is that :
Answer (d) & explanation
Nothing can be said about the gender mix of the party (d). Step 1: no male knew music. But only "many", not all, of the 20 women knew music. So some women may not know music. Step 2: the six chosen people knew no music. They could be all men, all women who do not know music, or a mix of both. Step 3: so option (a), only men, is not certain. Option (b), only non-musical women, is not certain. Option (c), both men and women, is also only possible. None of them must be true.
Tip: "many" and "some" never mean "all". When a group is chosen by lottery, any combination that fits the facts is possible, so be slow to draw a conclusion.
Answer as per the official UPSC answer key.
Five people A, B, C, D and E are seated about a round table. Every chair is spaced equidistant from adjacent chairs.
- (i) C is seated next to A
- (ii) A is seated two seats from D
- (iii) B is not seated next to A
On the basis of above information, which of the following must be true ?
- 1. D is seated next to B
- 2. E is seated next to A
- 3. D and C are separated by two seats
Select the correct answer using the code given below :
Answer (b) & explanation
Statements 1 and 2 must be true (b). Step 1: with five seats, A has two neighbours. B cannot sit next to A, and D sits two seats away, so not next to A either. So A's neighbours are C and E. Statement 2 is true. Step 2: the two seats that are not next to A are next to each other. B and D take them. So D sits next to B, and statement 1 is true. Step 3: the order could be A, C, D, B, E or A, C, B, D, E. In the second case D and C are not two seats apart. So statement 3 need not be true.
Tip: in seating puzzles, place the person with the most rules first. Then try every arrangement left before saying something "must" be true.
Answer as per the official UPSC answer key.
There are five hobby clubs in a college — photography, yachting, chess, electronics and gardening. The gardening group meets every second day, the electronics group meets every third day, the chess group meets every fourth day, the yachting group meets every fifth day and the photography group meets every sixth day. How many times do all the five groups meet on the same day within 180 days?
Answer (d) & explanation
All five groups meet together 3 times (d). Step 1: the groups meet every 2, 3, 4, 5 and 6 days. They all meet on the same day only on days that are multiples of every one of these numbers. Step 2: find the LCM of 2, 3, 4, 5 and 6. 4 = 2 × 2 and 6 = 2 × 3, so LCM = 2 × 2 × 3 × 5 = 60. They all meet every 60 days. Step 3: within 180 days that is days 60, 120 and 180, so 180 ÷ 60 = 3 times. Option (b), 18, comes from dividing by 10 by mistake. Options (a) and (c) do not fit.
Tip: "when do things happen together again" is almost always an LCM question.
2 × 3 × 4 × 5 × 6 = 720 is not the LCM. Use the LCM.
Answer as per the official UPSC answer key.
There are some nectar-filled flowers on a tree and some bees are hovering on it. If one bee lands on each flower, one bee will be left out. If two bees land on each flower, one flower will be left out. The number of flowers and bees respectively are :
Answer (c) & explanation
There are 3 flowers and 4 bees (c). Step 1: one bee per flower leaves one bee out. So bees = flowers + 1. Step 2: two bees per flower leaves one flower empty. So bees = 2 × (flowers − 1). Step 3: put them together: f + 1 = 2f − 2, so f = 3 and bees = 4. Check: 4 bees on 3 flowers leaves 1 bee over, and 2 bees each on 2 flowers uses all 4 bees with 1 flower empty. Option (a), 2 and 4, fails the first rule. Options (b) and (d) give fewer bees than flowers, which breaks the first rule.
Tip: you can skip the algebra by testing each option against both rules. The one that passes both is the answer.
(d) swaps the order. The question asks for flowers first.
Answer as per the official UPSC answer key.
There are five persons in a group — P, Q, R, S and T. The group has one doctor, one lawyer and one artist. P and S are unmarried students. T is a man married to one of the group members. Q is the brother of P and is neither doctor nor artist. R is not doctor.
Who is the doctor ?
Answer (a) & explanation
T is the doctor (a). Step 1: P and S are students, so they have no jobs. The doctor, lawyer and artist must be Q, R and T. Step 2: Q is neither the doctor nor the artist, so Q is the lawyer. Step 3: R is not the doctor, so R is the artist. That leaves T as the doctor. Options (b) P and (d) R are ruled out above, and (c) Q is the lawyer.
Tip: in grid puzzles, first remove the people who cannot hold any job. Then use the "is not" clues one at a time. Each clue usually fixes one more person. Make a small table of names and jobs and cross out boxes as you go.
Answer as per the official UPSC answer key.
(Same information as the question above.)
Who is the artist ?
Answer (c) & explanation
R is the artist (c). Step 1: P and S are students, so the three jobs belong to Q, R and T. Step 2: Q is neither the doctor nor the artist, so Q is the lawyer. Step 3: R is not the doctor. The only job left for R is artist, and T is the doctor. So option (c) is right. Option (a) P is a student and has no job. Option (b) Q is the lawyer. Option (d) T is the doctor.
Tip: linked questions share one grid. Solve the grid fully once, then answer every question from it. This saves time and avoids answering the same puzzle in different ways.
Answer as per the official UPSC answer key.
(Same information as the question above.)
Who is the spouse of R ?
Answer (b) & explanation
R's spouse is T (b). Step 1: T is a man married to someone in the group. Step 2: P and S are unmarried students, so they cannot be T's spouse. Q is the brother of P, so Q is a man, and here the married couple is taken as a man and a woman. Step 3: that leaves R as T's wife. So R's spouse is T. Option (a) P and option (d) S are unmarried. Option (c) Q is a man and P's brother, so he is not the spouse.
Tip: relation clues like "brother" also tell you a person's gender. Note every such hint; it is often the key that settles a marriage question.
Answer as per the official UPSC answer key.
(Same information as the question above.)
Who is the lawyer ?
Answer (b) & explanation
Q is the lawyer (b). Step 1: the jobs are doctor, lawyer and artist. P and S are students, so the jobs belong to Q, R and T. Step 2: Q is neither doctor nor artist. The only job left for Q is lawyer. Step 3: check the rest. R is not the doctor, so R is the artist and T is the doctor. Option (a) P and option (d) S are students. Option (c) R is the artist.
Tip: a clue that rules out two of three choices fixes the third straight away. Look for such clues first. Here the clue about Q settles the lawyer before you need anything else.
Answer as per the official UPSC answer key.
(Same information as the question above.)
Who of the following is definitely a man ?
Answer (c) & explanation
Q is definitely a man (c). Step 1: the puzzle says Q is "the brother of P". A brother is male, so Q is certainly a man. Step 2: T is also described as a man. But T is not one of the options, apart from "None of the above", which is wrong because Q qualifies. Step 3: the genders of P and S are never given. P could be Q's brother or sister, and S could be either. So options (a) and (b) are not certain. Option (d) fails because Q is a man.
Tip: "definitely" means the facts must prove it. Do not assume gender from names, jobs or seating; only words like brother, wife or "a man" count.
Answer as per the official UPSC answer key.
There is an order of 19000 quantity of a particular product from a customer. The firm produces 1000 quantity of that product per day out of which 5% are unfit for sale. In how many days will the order be completed?
Answer (c) & explanation
The order takes 20 days (c). Step 1: the firm makes 1000 pieces a day, but 5% are unfit. Good pieces per day = 95% of 1000 = 950. Step 2: the customer needs 19,000 good pieces. Days = 19,000 ÷ 950 = 20. Step 3: option (b), 19 days, is the trap: it divides 19,000 by 1000 and forgets the faulty pieces. Option (a), 18, is even less. Option (d), 22, is too many.
Tip: always work with the useful output, after removing waste or defects. A quick check: 950 × 20 = 19,000, which matches the order exactly.
Answer as per the official UPSC answer key.
Read the passage
Biomass as fuel for power, heat, and transport has the highest mitigation potential of all renewable sources. It comes from agriculture and forest residues as well as from energy crops. The biggest challenge in using biomass residues is a long-term reliable supply delivered to the power plant at reasonable costs; the key problems are logistical constraints and the costs of fuel collection. Energy crops, if not managed properly, compete with food production and may have undesirable impacts on food prices. Biomass production is also sensitive to the physical impacts of a changing climate.
Projections of the future role of biomass are probably overestimated, given the limits to the sustainable biomass supply, unless breakthrough technologies substantially increase productivity. Climate-energy models project that biomass use could increase nearly four-fold to around 150 — 200 exajoules, almost a quarter of world primary energy in 2050. However the maximum sustainable technical potential of biomass resources (both residues and energy crops) without disruption of food and forest resources ranges from 80 — 170 exajoules a year by 2050, and only part of this is realistically and economically feasible. In addition, some climate models rely on biomass-based carbon capture and storage, an unproven technology, to achieve negative emissions and to buy some time during the first half of the century.
Some liquid biofuels such as corn-based ethanol, mainly for transport, may aggravate rather than ameliorate carbon emissions on a life-cycle basis. Second generation biofuels, based on ligno-cellulosic feedstocks — such as straw, bagasse, grass and wood — hold the promise of sustainable production that is high-yielding and emit low levels of greenhouse gases, but these are still in the R & D stage.
What is/are the present constraint/constraints in using biomass as fuel for power generation ?
- 1. Lack of sustainable supply of biomass
- 2. Biomass production competes with food production
- 3. Bio-energy may not always be low carbon on a life-cycle basis
Select the correct answer using the code given below :
Answer (d) & explanation
All three constraints are right (d). Step 1: the passage mentions limits to "sustainable biomass supply". So statement 1, lack of a steady supply, is a constraint. Step 2: it says energy crops "compete with food production". So statement 2 is a constraint too. Step 3: it adds that biofuels "may aggravate" emissions "on a life-cycle basis". So bio-energy is not always low carbon, and statement 3 is right as well. Options (a), (b) and (c) each leave out at least one of the stated limits.
Tip: when every statement matches a line in the passage, pick "all of the above". Do not leave one out just because the full option seems too easy.
Answer as per the official UPSC answer key.
Read the passage
Biomass as fuel for power, heat, and transport has the highest mitigation potential of all renewable sources. It comes from agriculture and forest residues as well as from energy crops. The biggest challenge in using biomass residues is a long-term reliable supply delivered to the power plant at reasonable costs; the key problems are logistical constraints and the costs of fuel collection. Energy crops, if not managed properly, compete with food production and may have undesirable impacts on food prices. Biomass production is also sensitive to the physical impacts of a changing climate.
Projections of the future role of biomass are probably overestimated, given the limits to the sustainable biomass supply, unless breakthrough technologies substantially increase productivity. Climate-energy models project that biomass use could increase nearly four-fold to around 150 — 200 exajoules, almost a quarter of world primary energy in 2050. However the maximum sustainable technical potential of biomass resources (both residues and energy crops) without disruption of food and forest resources ranges from 80 — 170 exajoules a year by 2050, and only part of this is realistically and economically feasible. In addition, some climate models rely on biomass-based carbon capture and storage, an unproven technology, to achieve negative emissions and to buy some time during the first half of the century.
Some liquid biofuels such as corn-based ethanol, mainly for transport, may aggravate rather than ameliorate carbon emissions on a life-cycle basis. Second generation biofuels, based on ligno-cellulosic feedstocks — such as straw, bagasse, grass and wood — hold the promise of sustainable production that is high-yielding and emit low levels of greenhouse gases, but these are still in the R & D stage.
Which of the following can lead to food security problem ?
- 1. Using agricultural and forest residues as feedstock for power generation
- 2. Using biomass for carbon capture and storage
- 3. Promoting the cultivation of energy crops
Select the correct answer using the code given below :
Answer (b) & explanation
Only promoting energy crops threatens food security (b). Step 1: the passage says energy crops "compete with food production and may have undesirable impacts on food prices". So statement 3 is a food security risk. Step 2: agricultural and forest residues (statement 1) are left over after the harvest. Using them takes no food away. Step 3: carbon capture and storage with biomass (statement 2) is described as an unproven technology. It is a climate issue, not a food issue. So options (a), (c) and (d) fail.
Tip: link each statement to the exact problem the passage pins on it. Residues and waste are usually shown as the "safe" choice in biomass passages.
Answer as per the official UPSC answer key.
Read the passage
Biomass as fuel for power, heat, and transport has the highest mitigation potential of all renewable sources. It comes from agriculture and forest residues as well as from energy crops. The biggest challenge in using biomass residues is a long-term reliable supply delivered to the power plant at reasonable costs; the key problems are logistical constraints and the costs of fuel collection. Energy crops, if not managed properly, compete with food production and may have undesirable impacts on food prices. Biomass production is also sensitive to the physical impacts of a changing climate.
Projections of the future role of biomass are probably overestimated, given the limits to the sustainable biomass supply, unless breakthrough technologies substantially increase productivity. Climate-energy models project that biomass use could increase nearly four-fold to around 150 — 200 exajoules, almost a quarter of world primary energy in 2050. However the maximum sustainable technical potential of biomass resources (both residues and energy crops) without disruption of food and forest resources ranges from 80 — 170 exajoules a year by 2050, and only part of this is realistically and economically feasible. In addition, some climate models rely on biomass-based carbon capture and storage, an unproven technology, to achieve negative emissions and to buy some time during the first half of the century.
Some liquid biofuels such as corn-based ethanol, mainly for transport, may aggravate rather than ameliorate carbon emissions on a life-cycle basis. Second generation biofuels, based on ligno-cellulosic feedstocks — such as straw, bagasse, grass and wood — hold the promise of sustainable production that is high-yielding and emit low levels of greenhouse gases, but these are still in the R & D stage.
In the context of using biomass, which of the following is/are the characteristic/characteristics of the sustainable production of biofuel ?
- 1. Biomass as a fuel for power generation could meet all the primary energy requirements of the world by 2050
- 2. Biomass as a fuel for power generation does not necessarily disrupt food and forest resources
- 3. Biomass as a fuel for power generation could help in achieving negative emissions, given certain nascent technologies
Select the correct answer using the code given below :
Answer (c) & explanation
Statements 2 and 3 are right (c). Step 1: the passage says 80 to 170 exajoules a year could come from biomass "without disruption of food and forest resources". So statement 2 holds. Step 2: biomass with carbon capture can give "negative emissions", using nascent technologies. So statement 3 holds. Step 3: statement 1 says biomass could meet all the world's primary energy needs by 2050. The passage gives it about a quarter. So statement 1 is wrong, and options (a), (b) and (d) fail.
Tip: numbers are a common trap. When a statement says "all" and the passage gives a fraction, reject it.
Answer as per the official UPSC answer key.
Read the passage
Biomass as fuel for power, heat, and transport has the highest mitigation potential of all renewable sources. It comes from agriculture and forest residues as well as from energy crops. The biggest challenge in using biomass residues is a long-term reliable supply delivered to the power plant at reasonable costs; the key problems are logistical constraints and the costs of fuel collection. Energy crops, if not managed properly, compete with food production and may have undesirable impacts on food prices. Biomass production is also sensitive to the physical impacts of a changing climate.
Projections of the future role of biomass are probably overestimated, given the limits to the sustainable biomass supply, unless breakthrough technologies substantially increase productivity. Climate-energy models project that biomass use could increase nearly four-fold to around 150 — 200 exajoules, almost a quarter of world primary energy in 2050. However the maximum sustainable technical potential of biomass resources (both residues and energy crops) without disruption of food and forest resources ranges from 80 — 170 exajoules a year by 2050, and only part of this is realistically and economically feasible. In addition, some climate models rely on biomass-based carbon capture and storage, an unproven technology, to achieve negative emissions and to buy some time during the first half of the century.
Some liquid biofuels such as corn-based ethanol, mainly for transport, may aggravate rather than ameliorate carbon emissions on a life-cycle basis. Second generation biofuels, based on ligno-cellulosic feedstocks — such as straw, bagasse, grass and wood — hold the promise of sustainable production that is high-yielding and emit low levels of greenhouse gases, but these are still in the R & D stage.
With reference to the passage, following assumptions have been made :
- 1. Some climate-energy models suggest that the use of biomass as a fuel for power generation helps in mitigating greenhouse gas emissions
- 2. It is not possible to use biomass as a fuel for power generation without disrupting food and forest resources
Which of these assumptions is/are valid ?
Answer (a) & explanation
Only assumption 1 is valid (a). Step 1: the passage says climate-energy models rely on biomass for "negative emissions", and that it has "the highest mitigation potential". So some models do see biomass as helping to cut greenhouse gases. Assumption 1 holds. Step 2: assumption 2 says biomass power is impossible without disrupting food and forest. But the passage says a large potential exists "without disruption of food and forest resources". So 2 contradicts the passage. Step 3: so options (b), (c) and (d) fail.
Tip: when an assumption directly clashes with a quoted line, it is never valid. Look for the line that the statement contradicts.
Answer as per the official UPSC answer key.
Read the passage
We are witnessing a dangerous dwindling of biodiversity in our food supply. The green revolution is a mixed blessing. Over time farmers have come to rely heavily on broadly adapted, high yield crops to the exclusion of varieties adapted to the local conditions. Monocropping vast fields with the same genetically uniform seeds helps boost yield and meet immediate hunger needs. Yet high-yield varieties are also genetically weaker crops that require expensive chemical fertilizers and toxic pesticides. In our focus on increasing the amount of food we produce today, we have accidentally put ourselves at risk for food shortages in future.
Which among the following is the most logical and critical inference that can be made from the above passage ?
Answer (d) & explanation
The best inference is that the green revolution can threaten biodiversity and food security in the long run (d). Step 1: the passage calls the green revolution a "mixed blessing". Uniform high-yield crops cut biodiversity and may lead to "food shortages in future". Option (d) says exactly this. Step 2: option (a) says we use fertilisers "only due to green revolution". The word "only" goes too far. Option (c) says monocropping is "the only way" to food security, which the passage does not claim. Step 3: option (b) repeats a detail from the passage, not an inference.
Tip: a good inference joins the passage's warning to its consequence. Options with "only" are usually traps.
Answer as per the official UPSC answer key.
A class starts at 11:00 am and lasts till 2:27 pm. Four periods of equal duration are held during this interval. After every period, a rest of 5 minutes is given to the students. The exact duration of each period is :
Answer (a) & explanation
Each period lasts 48 minutes (a). Step 1: from 11:00 am to 2:27 pm is 3 hours 27 minutes = 207 minutes. Step 2: four periods have three breaks between them, because the class ends with the last period. Breaks = 3 × 5 = 15 minutes. Step 3: 4 periods = 207 − 15 = 192 minutes, so each period = 192 ÷ 4 = 48 minutes. Counting four breaks by mistake gives about 46.75 minutes, which matches no option. Options (b), (c) and (d) are all too long.
Tip: in "gaps between items" problems, n items have n − 1 gaps, like fence posts. Check: 4 × 48 + 15 = 207, which matches.
counting 4 breaks gives 46·75, which is not an option. That tells you the last break is not inside the class time.
Answer as per the official UPSC answer key.
Four friends A, B, C and D need to cross a bridge. A maximum of two persons can cross it at a time. It is night and they just have one lamp. Persons that cross the bridge must carry the lamp to find the way. A pair must walk together at the speed of slower person. After crossing the bridge, the person having faster speed in the pair will return with the lamp each time to accompany another person in the group. Finally, the lamp has to be returned at the original place and the person who returns the lamp has to cross the bridge again without lamp. To cross the bridge, the time taken by them is as follows : A: 1 minute, B: 2 minutes, C: 7 minutes and D: 10 minutes. What is the total minimum time required by all the friends to cross the bridge ?
Answer (a) & explanation
The minimum time is 23 minutes (a). Step 1: the rule says the faster person of each pair brings the lamp back. So A, the fastest (1 minute), should walk with everyone. Step 2: A + D cross (10), A returns (1), A + C cross (7), A returns (1), A + B cross (2). That is 21 minutes, and all four are across. Step 3: the puzzle adds that the lamp must be returned to the start, and the person who returns it must cross again without the lamp. A returns (1) and crosses back (1): 21 + 2 = 23 minutes. Option (c), 21, forgets this last rule. Options (b) and (d) do not follow the rules.
Tip: read every rule to the end; the last line often changes the answer.
the usual 17-minute trick (C and D crossing together) is not allowed here, because the faster person must return each time.
Answer as per the official UPSC answer key.
30 g of sugar was mixed in 180 ml water in a vessel A, 40 g of sugar was mixed in 280 ml of water in vessel B and 20 g of sugar was mixed in 100 ml of water in vessel C. The solution in vessel B is :
Answer (d) & explanation
Vessel B is less sweet than vessel C (d). Step 1: sweetness = sugar ÷ water. A = 30/180 = 1/6. B = 40/280 = 1/7. C = 20/100 = 1/5. Step 2: compare the fractions. 1/5 is bigger than 1/6, which is bigger than 1/7. So C is sweetest and B is least sweet. Step 3: so B is less sweet than C, option (d). Option (a) says the opposite. Option (b) is wrong because B is less sweet than A too. Option (c) is wrong because B and C are not equal.
Tip: to compare mixtures, turn each into "per unit" form and simplify. With the same numerator 1, a smaller denominator means a stronger mixture.
Answer as per the official UPSC answer key.
In aid of charity, every student in a class contributes as many rupees as the number of students in that class. With the additional contribution of Rs. 2 by one student only, the total collection is Rs. 443. Then how many students are there in the class?
Answer (b) & explanation
There are 21 students (b). Step 1: each student gives as many rupees as there are students. With n students, the total is n × n = n². Step 2: one student gives Rs 2 extra, so n² + 2 = 443, which gives n² = 441. Step 3: 21 × 21 = 441, so n = 21. Option (a), 12, gives only 144. Options (c) 43 and (d) 45 are traps built from the digits of 443 and 441.
Tip: when a total is "n times n", look for a perfect square near the number. Learning squares up to 30 by heart saves a lot of time in CSAT. Check: 21 × 21 + 2 = 443, which matches.
Answer as per the official UPSC answer key.
Anita's mathematics test had 70 problems carrying equal marks i.e., 10 arithmetic, 30 algebra and 30 geometry. Although she answered 70% of the arithmetic, 40% of the algebra and 60% of the geometry problems correctly, she did not pass the test because she got less than 60% marks. The number of more questions she would have to answer correctly to earn a 60% passing marks is :
Answer (b) & explanation
She needed 5 more correct answers (b). Step 1: count her correct answers. Arithmetic: 70% of 10 = 7. Algebra: 40% of 30 = 12. Geometry: 60% of 30 = 18. Total = 37. Step 2: passing needs 60% of 70 = 42 correct answers. Step 3: she needs 42 − 37 = 5 more. Option (a), 1, is too few. Option (c), 7, and option (d), 9, are too many. Since all questions carry equal marks, you can count questions instead of marks.
Tip: work out each part separately and then add. Do not average the percentages (70, 40 and 60), because each section has a different number of questions.
averaging the three percentages ignores the different section sizes.
Answer as per the official UPSC answer key.
In a class, there are 18 very tall boys. If these constitute three-fourths of the boys and the total number of boys is two-thirds of the total number of students in the class, what is the number of girls in the class?
Answer (b) & explanation
There are 12 girls (b). Step 1: 18 tall boys are three-fourths of the boys. So boys = 18 ÷ 3/4 = 24. Step 2: boys are two-thirds of all students. So students = 24 ÷ 2/3 = 36. Step 3: girls = 36 − 24 = 12. Option (a), 6, is a quarter of the boys, the boys who are not tall. Option (c), 18, is the number of tall boys. Option (d), 21, does not fit.
Tip: "x is a fraction of y" means y = x ÷ fraction. Work backwards one step at a time from the number you know. Check: girls are 12 of 36, which is one-third, the remaining part.
Answer as per the official UPSC answer key.
Consider the following statements :
- 1. Either A and B are of the same age or A is older than B
- 2. Either C and D are of the same age or D is older than C
- 3. B is older than C
Which of the following conclusions can be drawn from the above statements ?
Answer (d) & explanation
A is older than C (d). Step 1: write each statement as a sign. Statement 1: A is the same age as or older than B, so A ≥ B. Statement 2: D ≥ C. Statement 3: B > C. Step 2: join them: A ≥ B and B > C, so A > C for certain. Step 3: test the others. Option (a), A older than B, is only possible, since A and B may be equal. Option (c), D older than C, is also only possible, since they may be equal. Option (b), B and D the same age, is never linked by any statement.
Tip: turn age words into ≥ and > signs. A chain with a strict ">" anywhere gives a strict ">" at the end.
Answer as per the official UPSC answer key.
The monthly average salary paid to all the employees of a company was Rs. 5000. The monthly average salary paid to male and female employees was Rs. 5200 and Rs. 4200 respectively. Then the percentage of males employed in the company is :
Answer (b) & explanation
Males are 80% of the staff (b). Step 1: use alligation. The overall average is Rs 5000. Males earn Rs 5200, which is 200 above it. Females earn Rs 4200, which is 800 below it. Step 2: the counts are in the reverse ratio of these gaps. Males : females = 800 : 200 = 4 : 1. Step 3: males = 4 out of 5 = 80%. Option (a), 75%, would give an average of 4950. Options (c) and (d) give averages above 5000.
Tip: in mixture averages, the bigger group sits closer to the overall average. Since 5000 is much closer to 5200, males must be the large majority.
Answer as per the official UPSC answer key.
Six boxes A, B, C, D, E and F have been painted with six different colours viz., violet, indigo, blue, green, yellow and orange and arranged from left to right (not necessarily either kept or painted with the colours in the same order). Each box contains a ball of any one of the following six games: cricket, hockey, tennis, golf, football and volleyball (not necessarily in the same order). The golf ball is in violet box and is not in the box D. The box A which contains tennis ball is orange in colour and is at the extreme right. The hockey ball is neither in box D nor in box E. The box C having cricket ball is painted green. The hockey ball is neither in the box painted blue nor in the box painted yellow. The box C is fifth from right and next to box B. The box B contains volleyball. The box containing the hockey ball is between the boxes containing golf ball and volleyball.
Which one of the following boxes contains the golf ball ?
Answer (b) & explanation
The golf ball is in box E (b). Step 1: box A has tennis and is orange, at the far right. Box C has cricket and is green, fifth from the right. Box B, next to C, has volleyball. Step 2: that leaves golf, hockey and football for D, E and F. Golf is not in D. Hockey is in neither D nor E, so hockey is in F. Step 3: golf cannot go in D, so golf is in E, and football is in D. The violet box is E. Option (a) F has hockey. Option (c) D has football. Option (d) fails because E works.
Tip: in box puzzles, place the fixed facts first. Then use "not" clues to fill the last few gaps.
Answer as per the official UPSC answer key.
(Same information as the question above.)
Which of the following statements is/are correct ?
Answer (b) & explanation
F is painted indigo (b). Step 1: A is orange, C is green, and E (golf) is violet. Indigo, blue and yellow are left for B, D and F. Step 2: F holds the hockey ball. The hockey ball is in neither the blue nor the yellow box. So F must be indigo. Step 3: B and D share blue and yellow, but no clue says which is which. So option (a), D yellow, and option (c), B blue, are only possible, not certain. Option (d), "all of the above", fails too.
Tip: "is/are correct" in puzzles means "must be correct". If a fact could go either way, it does not count as correct.
Answer as per the official UPSC answer key.
(Same information as the question above.)
The football is in the box of which colour ?
Answer (c) & explanation
The colour of the football box cannot be determined (c). Step 1: from the earlier steps, the football is in box D. Step 2: F is indigo, so D and B share blue and yellow. Step 3: no clue tells us whether D is blue or yellow. The hockey rule fixes only F. So option (a) yellow and option (d) blue are both possible but not certain. Option (b), indigo, is wrong because F is indigo.
Tip: when two items can swap places with no rule broken, the answer is "cannot be determined". Before you choose it, check that you have used every clue. Here no clue links D or B to blue or yellow.
Answer as per the official UPSC answer key.
Two numbers X and Y are respectively 20% and 28% less than a third number Z. By what percentage is the number Y less than the number X?
Answer (b) & explanation
Y is 10% less than X (b). Step 1: take Z = 100. Then X is 20% less, so X = 80. Y is 28% less, so Y = 72. Step 2: Y is 80 − 72 = 8 less than X. Step 3: the question asks how much less than X, so the base is X. 8 ÷ 80 = 10%. Option (d), 8%, is the trap: it divides by 100, the base of Z. Option (a), 12%, and option (c), 9%, do not fit.
Tip: in percentage comparisons, always divide by the number after "than". Taking 100 as the starting value makes these questions quick.
28 – 20 = 8% uses Z as the base.
Answer as per the official UPSC answer key.
A daily train is to be introduced between station A and station B starting from each end at 6 AM and the journey is to be completed in 42 hours. What is the number of trains needed in order to maintain the shuttle service ?
Answer (c) & explanation
1. Day 1, 6 AM: one train leaves A and one leaves B. That is 2 trains.
2. 42 hours = 1 day and 18 hours, so these trains arrive at midnight at the end of Day 2. On Day 2 at 6 AM they are still running, so 2 more trains are needed.
3. Day 3, 6 AM: the Day 1 trains have arrived and can go back. No new train is needed after this.
4. Total = 4 trains.
Answer as per the official UPSC answer key.
A piece of tin is in the form of a rectangle having length 12 cm and width 8 cm. This is used to construct a closed cube. The side of the cube is :
Answer (c) & explanation
The side of the cube is 4 cm (c). Step 1: the tin sheet's area is 12 × 8 = 96 cm². Step 2: a closed cube has 6 equal square faces. So each face = 96 ÷ 6 = 16 cm². Step 3: 16 = 4 × 4, so each side is 4 cm. Option (a), 2 cm, gives only 24 cm² of surface. Option (b), 3 cm, gives 54 cm². Option (d), 6 cm, would need 216 cm², more than the sheet.
Tip: the surface area of a cube is 6 × side × side. When a sheet is "used to make" a solid, set the sheet's area equal to the solid's surface area, not its volume.
Answer as per the official UPSC answer key.
In a question paper there are five questions to be attempted and answer to each question has two choices — True (T) or False (F). It is given that no two candidates have given the answers to the five questions in an identical sequence. For this to happen, the maximum number of candidates is :
Answer (d) & explanation
At most 32 candidates (d). Step 1: each question has 2 possible answers, True or False. Step 2: for five questions, the number of different answer patterns is 2 × 2 × 2 × 2 × 2 = 32. Step 3: if no two candidates may have the same pattern, there can be at most 32 candidates. Option (a), 10, is 2 × 5, a common mistake of multiplying instead of raising to the power. Options (b) 18 and (c) 26 do not fit.
Tip: when each of n choices has k options, the number of combinations is k multiplied by itself n times. For yes/no questions that is 2, 4, 8, 16, 32 and so on.
Answer as per the official UPSC answer key.
Read the passage
By killing transparency and competition, crony capitalism is harmful to free enterprise, opportunity and economic growth. Crony capitalism, where rich and the influential are alleged to have received land and natural resources and various licences in return for payoffs to venal politicians, is now a major issue to be tackled. One of the greatest dangers to growth of developing economies like India is the middle-income trap where crony capitalism creates oligarchies that slow down the growth.
Which among the following is the most logical corollary to the above passage ?
Answer (c) & explanation
The logical corollary is the need for transparency and financial inclusion (c). Step 1: the passage says crony capitalism kills transparency and competition and keeps the poor away from licences and credit. Step 2: so the natural follow-up is more transparency and wider access to finance, which is option (c). Step 3: option (a), more welfare schemes, is never discussed. Option (b) mentions licences for the poor but not the transparency problem. Option (d), manufacturing over services, is not discussed at all.
Tip: a corollary is the solution that follows directly from the problem the passage names. Match the cure to the disease, here secrecy and exclusion.
Answer as per the official UPSC answer key.
Read the passage
Climate adaptation may be rendered ineffective if policies are not designed in the context of other development concerns. For instance, a comprehensive strategy that seeks to improve food security in the context of climate change may include a set of coordinated measures related to agricultural extension, crop diversification, integrated water and pest management and agricultural information services. Some of these measures may have to do with climate changes and others with economic development.
What is the most logical and rational inference that can be made from the above passage ?
Answer (d) & explanation
Climate adaptation should be examined together with other development options (d). Step 1: the passage says adaptation fails "if policies are not designed in the context of other development concerns". That is option (d). Step 2: option (c) says every development activity is linked to adaptation. The word "every" goes too far. Step 3: option (b) compares how complex food security and adaptation are, which the passage never does. Option (a), that adaptation is hard in developing countries, is not the main point.
Tip: the safest inference restates the author's main condition. Reject options with extreme words like "every" or comparisons the author never makes.
Answer as per the official UPSC answer key.
Read the passage
Understanding of the role of biodiversity in the hydrological cycle enables better policy-making. The term biodiversity refers to the variety of plants, animals, microorganisms, and the ecosystems in which they occur. Water and biodiversity are interdependent. In reality, the hydrological cycle decides how biodiversity functions. In turn, vegetation and soil drive the movement of water. Every glass of water we drink has, at least in part, passed through fish, trees, bacteria, soil and other organisms. Passing through these ecosystems, it is cleansed and made fit for consumption. The supply of water is a critical service that the environment provides.
Which among the following is the most critical inference that can be made from the above passage ?
Answer (a) & explanation
The best inference is that biodiversity keeps nature's water cycle going (a). Step 1: the passage says vegetation and soil "drive the movement of water", and ecosystems cleanse it. So living things sustain nature's water recycling. Step 2: option (b) says we cannot get drinking water without living things. The passage says water passes through organisms "at least in part", so "cannot" overstates it. Step 3: option (c), about organisms interacting, is true but beside the point. Option (d) is about how life began, which the passage does not discuss.
Tip: pick the option that sums up the passage's link. Options that go further than the passage, like "cannot", are traps.
Answer as per the official UPSC answer key.
Read the passage
In the last decade, the banking sector has been restructured with a high degree of automation and products that mainly serve middle-class and upper middle-class society. Today there is a need for a new agenda for the banking and non-banking financial services that does not exclude the common man.
Which one of the following is the message that is essentially implied in the above passage ?
Answer (d) & explanation
The implied message is the need to promote financial inclusion (d). Step 1: the passage says banking mainly serves the middle classes, and a new agenda must not "exclude the common man". That is financial inclusion. Step 2: option (a), more automation, is part of the problem the passage describes, not the cure. Step 3: option (b), restructuring the whole public finance system, goes beyond banking. Option (c), integrating banks and non-banks, is not raised.
Tip: financial inclusion means bringing the poor and rural people into banking: accounts, credit and insurance. Schemes like Jan Dhan accounts are real-life examples.
Answer as per the official UPSC answer key.
Read the passage
Safe and sustainable sanitation in slums has immeasurable benefits to women and girls in terms of their health, safety, privacy and dignity. However, women do not feature in most of the schemes and policies on urban sanitation. The fact that even now the manual scavenging exists, only goes to show that not enough has been done to promote pour-flush toilets and discontinue the use of dry latrines. A more sustained and rigorous campaign needs to be launched towards the right to sanitation on a very large scale. This should primarily focus on the abolition of manual scavenging.
With reference to the above passage, consider the following statements :
- 1. Urban sanitation problems can be fully solved by the abolition of manual scavenging only
- 2. There is a need to promote greater awareness on safe sanitation practices in urban areas
Which of the statements given above is/are correct?
Answer (b) & explanation
Only statement 2 is correct (b). Step 1: the passage calls for a "sustained and rigorous campaign" on sanitation. So more awareness about safe sanitation is needed, and statement 2 holds. Step 2: statement 1 says sanitation problems can be "fully solved" by abolishing manual scavenging "only". The passage makes abolition the main focus, but never says it alone fixes everything. Step 3: so statement 1 goes too far, and options (a), (c) and (d) fail.
Tip: strong words like "fully" and "only" turn a reasonable idea into a false statement. Manual scavenging is banned by a 2013 Act, but sanitation needs much more than one ban.
Answer as per the official UPSC answer key.
Read the passage
To understand the nature and quantity of Government proper for man, it is necessary to attend to his character. As nature created him for social life, she fitted him for the station she intended. In all cases she made his natural wants greater than his individual powers. No one man is capable, without the aid of society, of supplying his own wants, and those wants, acting upon every individual, impel the whole of them into society.
Which among the following is the most logical and rational inference that can be made from the above passage ?
Answer (d) & explanation
The best inference is that many natural wants pushed people into society (d). Step 1: the passage says human wants are greater than one person's powers. These wants "impel the whole of them into society". That is option (d). Step 2: option (b) says every society is always short of its wants. But the passage says individuals, not societies, fall short. Step 3: option (c), that social life is special to humans, states a fact without the reason. Option (a), that nature created diversity, is not discussed.
Tip: an inference should keep the author's cause and effect. Here the cause is many wants and the effect is social life.
Answer as per the official UPSC answer key.
Read the passage
The nature of the legal imperatives in any given state corresponds to the effective demands that state encounters, and that these, in their turn, depend, in a general way, upon the manner in which economic power is distributed in the society which the state controls.
The statement refers to :
Answer (b) & explanation
The statement shows the link between politics and economics (b). Step 1: it says laws follow the demands made on the state, and these depend "in a general way" on how economic power is spread. Step 2: so economics shapes politics, but only in a general way. That is a two-way relationship, not full control. Step 3: options (c) and (d) speak of one dominating the other, which "in a general way" does not support. Option (a), opposition between the two, is nowhere suggested.
Tip: soft words like "in a general way" or "to some extent" signal a link, not dominance. Choose the milder option when the author hedges.
Answer as per the official UPSC answer key.
Read the passage
About 15 per cent of global greenhouse gas emissions come from agricultural practices. This includes nitrous oxide from fertilizers; methane from livestock, rice production, and manure storage; and carbon dioxide (CO₂) from burning biomass, but this excludes CO₂ emissions from soil management practices, savannah burning and deforestation. Forestry, land use, and land-use change account for another 17 per cent of greenhouse gas emissions each year, three quarters of which come from tropical deforestation. The remainder is largely from draining and burning tropical peatland. About the same amount of carbon is stored in the world’s peatlands as is stored in the Amazon rainforest.
Which among the following is the most logical and rational inference that can be made from the above passage ?
Answer (b) & explanation
We must change our land use practices to fight climate change (b). Step 1: the passage says agriculture causes about 15% and land use change about 17% of greenhouse gas emissions. Together that is about a third. Step 2: so changing how we use land is a must, which is option (b). Step 3: option (a) wants organic farming "immediately… all over the world", which is far too extreme. Option (c), that there are no technical fixes, is not discussed. Option (d), that tropics are the main carbon store, is not stated.
Tip: agriculture and land use are big emission sources because of fertilisers, livestock and forest clearing. That is why climate plans stress forests and farming.
Answer as per the official UPSC answer key.
A person climbs a hill in a straight path from point 'O' on the ground in the direction of north-east and reaches a point 'A' after travelling a distance of 5 km. Then, from the point 'A' he moves to point 'B' in the direction of north-west. Let the distance AB be 12 km. Now, how far is the person away from the starting point 'O' ?
Answer (b) & explanation
He is 13 km from the start (b). Step 1: north-east and north-west are at right angles to each other. So O, A and B form a right-angled triangle. Step 2: square the two short sides and add them: 5 × 5 + 12 × 12 = 25 + 144 = 169. Step 3: 13 × 13 = 169, so the distance OB is 13 km. Option (a), 7 km, is 12 − 5. Option (c), 17 km, is 12 + 5. Option (d), 11 km, does not fit.
Tip: learn the common right-triangle sets: 3-4-5, 5-12-13, 8-15-17 and 7-24-25. Seeing 5 and 12 should make you think of 13 at once.
Answer as per the official UPSC answer key.
An agricultural field is in the form of a rectangle having length X1 meters and breadth X2 meters (X1 and X2 are variable). If X1 + X2 = 40 meters, then the area of the agricultural field will not exceed which one of the following values?
Answer (a) & explanation
The area cannot exceed 400 sq m (a). Step 1: length + breadth = 40 m. Step 2: for a fixed sum, the product is largest when the two parts are equal. So the best is 20 × 20. Step 3: maximum area = 400 sq m. Try others: 30 × 10 = 300 and 35 × 5 = 175, both smaller. So options (b) 300, (c) 200 and (d) 80 are possible areas, but the question asks for the value it will not exceed.
Tip: among rectangles with the same perimeter, the square has the largest area. This idea comes up often in CSAT.
Answer as per the official UPSC answer key.
The sum of the ages of 5 members comprising a family, 3 years ago was 80 years. The average age of the family today is the same as it was 3 years ago, because of an addition of a baby during the intervening period. How old is the baby?
Answer (b) & explanation
The baby is 1 year old (b). Step 1: three years ago, the 5 members' ages added to 80. So the average was 80 ÷ 5 = 16. Step 2: today each of the five is 3 years older. Their total = 80 + 5 × 3 = 95. Step 3: with the baby there are 6 members, and the average is still 16. So the total = 6 × 16 = 96. Baby = 96 − 95 = 1 year. Option (a), 6 months, and options (c) and (d) do not fit.
Tip: in age-average questions, work with totals, not averages. Every year adds 1 year to each person, so a group of n people gains n years in total each year.
Answer as per the official UPSC answer key.
The total emoluments of two persons are the same, but one gets allowances to the extent of 65% of his basic pay and the other gets allowances to the extent of 80% of his basic pay. The ratio of the basic pay of the former to the basic pay of the latter is :
Answer (d) & explanation
The ratio of their basic pays is 12 : 11 (d). Step 1: the first person's total is basic + 65% of basic = 1.65 × basic. The second person's total is 1.80 × basic. Step 2: the totals are equal, so 1.65 × B1 = 1.80 × B2. Step 3: B1 : B2 = 1.80 : 1.65. Multiply by 100 to get 180 : 165, then divide by 15 to get 12 : 11. The person with the smaller allowance must have the bigger basic pay. Option (a) 16 : 13 and option (b) 5 : 4 are traps from the 80 and 65 figures. Option (c) does not fit.
Tip: if a × X = b × Y, then X : Y = b : a. The ratio flips.
80 : 65 = 16 : 13 forgets that the total is basic + allowance.
Answer as per the official UPSC answer key.
A person is standing on the first step from the bottom of a ladder. If he has to climb 4 more steps to reach exactly the middle step, how many steps does the ladder have?
Answer (b) & explanation
The ladder has 9 steps (b). Step 1: he is on step 1 and climbs 4 more steps, so the middle step is step 5. Step 2: a middle step has the same number of steps below and above it. There are 4 steps below step 5. So there must be 4 above. Step 3: total = 4 + 1 + 4 = 9 steps. Option (a), 8, has no single middle step. Option (c), 10, also has no single middle step. Option (d), 11, would put the middle at step 6.
Tip: a "middle" item exists only when the total is odd. For an odd total n, the middle item is number (n + 1) ÷ 2. Here (9 + 1) ÷ 2 = 5, which checks out.
Answer as per the official UPSC answer key.
When three friends A, B and C met, it was found that each of them wore an outer garment of a different colour. In random order, the garments are: jacket, sweater and tie; and the colours are: blue, white and black. Their surnames in random order are: Ribeiro, Kumar and Singh. Further, we know that :
- 1. neither B nor Ribeiro wore a white sweater
- 2. C wore a tie
- 3. Singh's garment was not white
- 4. Kumar does not wear a jacket
- 5. Ribeiro does not like to wear the black colour
- 6. Each of the friends wore only one outer garment of only one colour
What is C's surname ?
Answer (a) & explanation
C's surname is Ribeiro (a). Step 1: someone wore the white sweater. It was not B (clue 1) and not C, who wore the tie (clue 2). So A wore the white sweater. Step 2: A is not Ribeiro (clue 1) and not Singh, whose garment was not white (clue 3). So A is Kumar. Step 3: clue 1 names B and Ribeiro as two different people. So B is not Ribeiro, which makes C Ribeiro and B Singh. Options (b) Kumar and (c) Singh belong to A and B. Option (d) fails because the clues settle it.
Tip: clues like "neither B nor Ribeiro" quietly tell you B and Ribeiro are different people. Use such hidden facts.
Answer as per the official UPSC answer key.
(Same information as the question above.)
What is the colour of the tie ?
Answer (b) & explanation
The tie is blue (b). Step 1: C wears the tie, and C is Ribeiro. Step 2: white is already A's colour, because A wore the white sweater. Step 3: Ribeiro does not wear black (clue 5). So the only colour left for the tie is blue. B, Singh, then wears the black jacket. Option (a), black, is ruled out by clue 5. Option (c), white, belongs to A. Option (d) fails because the colour is fixed.
Tip: once names and garments are fixed, colours fall into place quickly. Build a small table with rows for A, B and C and columns for surname, garment and colour. Fill it in as each clue settles a box.
Answer as per the official UPSC answer key.
(Same information as the question above.)
Who wore the sweater ?
Answer (a) & explanation
A wore the sweater (a). Step 1: someone wore a white sweater. Clue 1 says B did not wear it. Clue 2 says C wore a tie. So the white sweater belongs to A. Step 2: this also fixes the rest. A is Kumar, C (Ribeiro) wears the blue tie, and B (Singh) wears the black jacket. Kumar does not wear a jacket, which fits A wearing the sweater. Step 3: so option (b) B wears the jacket, and option (c) C wears the tie. Option (d) fails because the answer is clear.
Tip: in linked puzzles, the first fact you work out often answers a later question directly. Write down each solved fact as you go.
Answer as per the official UPSC answer key.
AB is a vertical trunk of a huge tree with A being the point where the base of the trunk touches the ground. Due to a cyclone, the trunk has been broken at C which is at a height of 12 meters, broken part is partially attached to the vertical portion of the trunk at C. If the end of the broken part B touches the ground at D which is at a distance of 5 meters from A, then the original height of the trunk is :
Answer (b) & explanation
The original height was 25 m (b). Step 1: the trunk breaks at C, 12 m high, and the top touches the ground 5 m from the base. The standing part (12 m), the ground distance (5 m) and the broken part form a right-angled triangle. Step 2: broken part = √(12 × 12 + 5 × 5) = √169 = 13 m. This is the 5-12-13 set. Step 3: original height = standing part + broken part = 12 + 13 = 25 m. Option (a), 20 m, and options (c) and (d) do not fit.
Tip: in broken-tree problems, the broken piece is the long side of the triangle. Add it back to the standing part to get the full height.
Answer as per the official UPSC answer key.
A person walks 12 km due north, then 15 km due east, after that 19 km due west and then 15 km due south. How far is he from the starting point ?
Answer (a) & explanation
He is 5 km from the start (a). Step 1: north–south: 12 km north, then 15 km south, leaves him 3 km south of the start. Step 2: east–west: 15 km east, then 19 km west, leaves him 4 km west. Step 3: 3 km south and 4 km west form a right angle. The straight-line distance is √(3 × 3 + 4 × 4) = √25 = 5 km. Option (b), 9 km, does not fit. Option (c), 37 km, adds some of the walks. Option (d), 61 km, adds all four walks, which is total distance, not displacement.
Tip: "how far from the start" means straight-line distance. Cancel opposite directions first, then use the right-angle rule.
Answer as per the official UPSC answer key.
A cube has all its faces painted with different colours. It is cut into smaller cubes of equal sizes such that the side of the small cube is one-fourth the big cube. The number of small cubes with only one of the sides painted is :
Answer (b) & explanation
24 small cubes have only one face painted (b). Step 1: each side is cut into 4, so the big cube becomes 4 × 4 × 4 = 64 small cubes. Step 2: on each face there are 4 × 4 = 16 small cubes. The ones on the edges of that face also touch another face. Only the inner 2 × 2 = 4 have just one painted side. Step 3: a cube has 6 faces, so 6 × 4 = 24. Option (a), 32, does not fit. Option (d), 8, is the number of corner cubes, which have three painted faces.
Tip: for a cube cut n × n × n, one-face cubes = 6 × (n − 2)². Corner cubes are always 8.
Answer as per the official UPSC answer key.
Ram and Shyam work on a job together for four days and complete 60% of it. Ram takes leave then and Shyam works for eight more days to complete the job. How long would Ram take to complete the entire job alone?
Answer (c) & explanation
Ram alone would take 10 days (c). Step 1: together, 60% in 4 days means 15% per day together. Step 2: Shyam alone finishes the last 40% in 8 days, so Shyam does 5% per day. Step 3: Ram's rate = 15% − 5% = 10% per day. The whole job takes Ram 100 ÷ 10 = 10 days. Option (a), 6 days, and option (b), 8 days, are too fast. Option (d), 11 days, is too slow.
Tip: turn work into "percent per day" or "units per day". Rates add when people work together, so you can subtract to find one person's rate. Check: Ram and Shyam do 10% + 5% = 15% a day, which matches.
Answer as per the official UPSC answer key.
A military code writes SYSTEM as SYSMET and NEARER as AENRER. Using the same code, FRACTION can be written as :
Answer (d) & explanation
FRACTION is written as CARFNOIT (d). Step 1: look at SYSTEM → SYSMET. Split it into halves: SYS | TEM. Each half is written backwards: SYS stays SYS, and TEM becomes MET. Step 2: check with NEARER → AENRER. NEA becomes AEN, and RER stays RER. The rule holds. Step 3: FRACTION splits into FRAC | TION. Reversed: CARF | NOIT, giving CARFNOIT. Option (a), CARFTION, reverses only the first half. Option (b), FRACNOIT, reverses only the second half. Option (c), NOITCARF, reverses the whole word.
Tip: in coding questions, test a rule on both examples before using it. Palindrome halves like SYS can hide the pattern.
Answer as per the official UPSC answer key.
If R and S are different integers both divisible by 5, then which of the following is not necessarily true?
Answer (b) & explanation
"R + S is divisible by 10" is not always true (b). Step 1: R and S are multiples of 5, so write R = 5a and S = 5b. Step 2: R − S = 5(a − b), divisible by 5. R × S = 25ab, divisible by 25. R² + S² = 25(a² + b²), divisible by 5. So options (a), (c) and (d) always hold. Step 3: R + S = 5(a + b). This is divisible by 10 only if a + b is even. Take R = 5 and S = 10. Then R + S = 15, which is not divisible by 10. So (b) is not necessarily true.
Tip: for "not necessarily true", one counter-example is enough. Try the smallest numbers that fit the rules.
Answer as per the official UPSC answer key.
How many numbers are there between 100 and 300 which either begin with or end with 2?
Answer (a) & explanation
There are 110 such numbers (a). Step 1: between 100 and 300, the numbers that begin with 2 are 200 to 299. That is 100 numbers. Step 2: numbers that end with 2 and begin with 1 are 102, 112, 122 and so on up to 192. That is 10 numbers. The ones ending in 2 that begin with 2, like 202, are already counted. Step 3: total = 100 + 10 = 110. Option (b), 111, counts something twice. Options (c) and (d) do not fit.
Tip: for "either… or" counts, add the two groups and subtract the overlap. Here we simply skipped the overlap. This rule is called inclusion–exclusion.
adding 100 + 20 counts 202, 212, … twice.
Answer as per the official UPSC answer key.
Read the passage
As we look to 2050, when we will need to feed two billion more people, the question of which diet is best has taken on new urgency. The foods we choose to eat in the coming decades will have dramatic ramifications for the planet. Simply put, a diet that revolves around meat and dairy, a way of eating that is on the rise throughout the developing world, will take a greater toll on the world’s resources than one that revolves around unrefined grains, nuts, fruits and vegetables.
What is the critical message conveyed by the above passage ?
Answer (a) & explanation
The critical message is that more animal-based food puts a bigger burden on natural resources (a). Step 1: the passage says a diet rich in meat and dairy "will take a greater toll on the world's resources". That is option (a). Step 2: option (b) says plant diets are best for health in developing countries. But the passage judges diets by their effect on the planet, not on health. Step 3: option (c), about people changing habits regardless of health, is not the point. Option (d), that we do not know the best diet, misses the main concern.
Tip: animal food needs much more land, water and feed per calorie than plant food. This is a common theme in climate passages.
Answer as per the official UPSC answer key.
Read the passage
All humans digest mother’s milk as infants, but until cattle began being domesticated 10,000 years ago, children once weaned no longer needed to digest milk. As a result, they stopped making the enzyme lactase, which breaks down the sugar lactose into simple sugars. After humans began herding cattle, it became tremendously advantageous to digest milk, and lactose tolerance evolved independently among cattle herders in Europe, the middle East and Africa. Groups not dependant on cattle, such as the Chinese and Thai, remain lactose intolerant.
Which among the following is the most logical assumption that can be made from the above passage ?
Answer (b) & explanation
The logical assumption is that a lasting change in food habits can bring a genetic change (b). Step 1: the passage says herding made milk a lasting food, and lactose tolerance evolved among herders. So a long-term diet change led to a genetic change. That is option (b). Step 2: option (a), about domestication 10,000 years ago, restates a fact rather than an assumption. Step 3: option (c) says only lactose-tolerant people get simple sugars, and option (d) says intolerant people cannot digest any dairy. Both overgeneralise; many people digest curd and cheese.
Tip: an assumption is the hidden link the author needs. Facts already stated in the passage are not assumptions.
Answer as per the official UPSC answer key.
Read the passage
“The conceptual difficulties in National Income comparisons between underdeveloped and industrialised countries are particularly serious because a part of the national output in various underdeveloped countries is produced without passing through the commercial channels.”
In the above statement, the author implies that :
Answer (b) & explanation
The author implies that a non-commercial sector makes income comparisons between countries difficult (b). Step 1: the passage says comparisons are hard "because a part of the national output… is produced without passing through the commercial channels". In poor countries, people grow and consume much of their own output. Step 2: so option (b) captures the point. Step 3: option (a) says the entire output in rich countries passes through markets, which is too extreme. Option (c) tells us what should happen, a prescription the author never makes. Option (d) calls it a sign of underdevelopment, which is not claimed.
Tip: GDP counts mostly market transactions, so unpaid home work and own-farm food are often missed.
Answer as per the official UPSC answer key.
Read the passage
An increase in human-made carbon dioxide in the atmosphere could initiate a chain reaction between plants and microorganisms that would unsettle one of the largest carbon reservoirs on the planet — soil. In a study, it was found that the soil, which contains twice the amount of carbon present in all plants and Earth’s atmosphere combined, could become increasingly volatile as people add more carbon dioxide to the atmosphere. This is largely because of increased plant growth. Although a greenhouse gas and a pollutant, carbon dioxide also supports plant growth. As trees and other vegetation flourish in a carbon dioxide-rich future, their roots could stimulate microbial activity in soil that may in turn accelerate the decomposition of soil carbon and its release into the atmosphere as carbon dioxide.
Which among the following is the most logical corollary to the above passage ?
Answer (d) & explanation
The best corollary is that more green cover could release carbon trapped in soil (d). Step 1: the passage says thriving vegetation feeds soil microbes, which "accelerate the decomposition of soil carbon". When soil carbon breaks down, carbon dioxide is released. So more plants could release soil carbon. That is option (d). Step 2: option (b) says humans are solely responsible for carbon dioxide, which the passage contradicts. Step 3: option (c) reverses the cause: plants feed the microbes, not the other way. Option (a) is true but not the passage's point.
Tip: a corollary follows from the passage's chain of cause and effect. Trace the chain carefully, plants to microbes to soil carbon.
Answer as per the official UPSC answer key.
Read the passage
Historically, the biggest challenge to world agriculture has been to achieve a balance between demand for and supply of food. At the level of individual countries, the demand-supply balance can be a critical policy issue for a closed economy, especially if it is a populous economy and its domestic agriculture is not growing sufficiently enough to ensure food supplies, on an enduring basis; it is not so much and not always, of a constraint for an open, and growing economy, which has adequate exchange surpluses to buy food abroad. For the world as a whole, supply-demand balance is always an inescapable prerequisite for warding off hunger and starvation. However, global availability of adequate supply does not necessarily mean that food would automatically move from countries of surplus to countries of deficit if the latter lack in purchasing power. The uneven distribution of hunger, starvation, under- or malnourishment, etc., at the world-level, thus owes itself to the presence of empty-pocket hungry mouths, overwhelmingly confined to the underdeveloped economies. Inasmuch as ‘a two-square meal’ is of elemental significance to basic human existence, the issue of worldwide supply of food has been gaining significance, in recent times; both because the quantum and the composition of demand has been undergoing big changes, and because, in recent years, the capabilities of individual countries to generate uninterrupted chain of food supplies have come under strain. Food production, marketing and prices, especially price-affordability by the poor in the developing world, have become global issues that need global thinking and global solutions.
According to the above passage, which of the following are the fundamental solutions for the world food security problem ?
- 1. Setting up more agro-based industries
- 2. Improving the price affordability by the poor
- 3. Regulating the conditions of marketing
- 4. Providing food subsidy to one and all
Select the correct answer using the code given below:
Answer (b) & explanation
Statements 2 and 3 are the fundamental solutions (b). Step 1: the closing line names "marketing and prices, especially price-affordability by the poor" as the key global issues. Step 2: so improving affordability for the poor (2) and regulating marketing conditions (3) are the solutions the passage points to. Step 3: setting up agro-based industries (1) and food subsidy for all (4) are not mentioned. So options (a), (c) and (d) fail.
Tip: "according to the passage" means stick to what is written. A food subsidy for "one and all" also sounds extreme; the passage stresses the poor. In India, the National Food Security Act targets about two-thirds of the population, not everyone.
Answer as per the official UPSC answer key.
Read the passage
Historically, the biggest challenge to world agriculture has been to achieve a balance between demand for and supply of food. At the level of individual countries, the demand-supply balance can be a critical policy issue for a closed economy, especially if it is a populous economy and its domestic agriculture is not growing sufficiently enough to ensure food supplies, on an enduring basis; it is not so much and not always, of a constraint for an open, and growing economy, which has adequate exchange surpluses to buy food abroad. For the world as a whole, supply-demand balance is always an inescapable prerequisite for warding off hunger and starvation. However, global availability of adequate supply does not necessarily mean that food would automatically move from countries of surplus to countries of deficit if the latter lack in purchasing power. The uneven distribution of hunger, starvation, under- or malnourishment, etc., at the world-level, thus owes itself to the presence of empty-pocket hungry mouths, overwhelmingly confined to the underdeveloped economies. Inasmuch as ‘a two-square meal’ is of elemental significance to basic human existence, the issue of worldwide supply of food has been gaining significance, in recent times; both because the quantum and the composition of demand has been undergoing big changes, and because, in recent years, the capabilities of individual countries to generate uninterrupted chain of food supplies have come under strain. Food production, marketing and prices, especially price-affordability by the poor in the developing world, have become global issues that need global thinking and global solutions.
According to the above passage, the biggest challenge to world agriculture is :
Answer (d) & explanation
The biggest challenge is to balance the demand for and supply of food (d). Step 1: the first sentence says: "the biggest challenge to world agriculture has been to achieve a balance between demand for and supply of food". Option (d) matches it word for word. Step 2: option (a), finding land and expanding food processing, is not called the biggest challenge. Step 3: option (b), ending hunger in poor countries, is a result of the imbalance, not the challenge named. Option (c), balancing food and non-food production, is not discussed.
Tip: when the passage states the answer directly, pick the option closest to its words. Do not overthink "biggest challenge" questions.
Answer as per the official UPSC answer key.
Read the passage
Historically, the biggest challenge to world agriculture has been to achieve a balance between demand for and supply of food. At the level of individual countries, the demand-supply balance can be a critical policy issue for a closed economy, especially if it is a populous economy and its domestic agriculture is not growing sufficiently enough to ensure food supplies, on an enduring basis; it is not so much and not always, of a constraint for an open, and growing economy, which has adequate exchange surpluses to buy food abroad. For the world as a whole, supply-demand balance is always an inescapable prerequisite for warding off hunger and starvation. However, global availability of adequate supply does not necessarily mean that food would automatically move from countries of surplus to countries of deficit if the latter lack in purchasing power. The uneven distribution of hunger, starvation, under- or malnourishment, etc., at the world-level, thus owes itself to the presence of empty-pocket hungry mouths, overwhelmingly confined to the underdeveloped economies. Inasmuch as ‘a two-square meal’ is of elemental significance to basic human existence, the issue of worldwide supply of food has been gaining significance, in recent times; both because the quantum and the composition of demand has been undergoing big changes, and because, in recent years, the capabilities of individual countries to generate uninterrupted chain of food supplies have come under strain. Food production, marketing and prices, especially price-affordability by the poor in the developing world, have become global issues that need global thinking and global solutions.
According to the above passage, which of the following helps/help in reducing hunger and starvation in the developing economies ?
- 1. Balancing demand and supply of food
- 2. Increasing imports of food
- 3. Increasing purchasing power of the poor
- 4. Changing the food consumption patterns and practices
Select the correct answer using the code given below :
Answer (c) & explanation
Statements 1 and 3 help reduce hunger (c). Step 1: the passage calls the balance of food demand and supply an "inescapable prerequisite". So statement 1 helps. Step 2: it says hunger comes from "empty-pocket hungry mouths". People are hungry because they cannot buy food. So raising the poor's purchasing power (3) helps. Step 3: increasing imports (2) needs money, so imports alone do not reach the poor. Changing food habits (4) is not suggested. So options (a), (b) and (d) fail.
Tip: this echoes Amartya Sen's idea of entitlement. Famines often happen not from a lack of food, but because the poor lack the income to buy it.
Answer as per the official UPSC answer key.
Read the passage
Historically, the biggest challenge to world agriculture has been to achieve a balance between demand for and supply of food. At the level of individual countries, the demand-supply balance can be a critical policy issue for a closed economy, especially if it is a populous economy and its domestic agriculture is not growing sufficiently enough to ensure food supplies, on an enduring basis; it is not so much and not always, of a constraint for an open, and growing economy, which has adequate exchange surpluses to buy food abroad. For the world as a whole, supply-demand balance is always an inescapable prerequisite for warding off hunger and starvation. However, global availability of adequate supply does not necessarily mean that food would automatically move from countries of surplus to countries of deficit if the latter lack in purchasing power. The uneven distribution of hunger, starvation, under- or malnourishment, etc., at the world-level, thus owes itself to the presence of empty-pocket hungry mouths, overwhelmingly confined to the underdeveloped economies. Inasmuch as ‘a two-square meal’ is of elemental significance to basic human existence, the issue of worldwide supply of food has been gaining significance, in recent times; both because the quantum and the composition of demand has been undergoing big changes, and because, in recent years, the capabilities of individual countries to generate uninterrupted chain of food supplies have come under strain. Food production, marketing and prices, especially price-affordability by the poor in the developing world, have become global issues that need global thinking and global solutions.
The issue of worldwide supply of food has gained importance mainly because of :
- 1. overgrowth of the population worldwide
- 2. sharp decline in the area of food production
- 3. limitation in the capabilities for sustained supply of food
Select the correct answer using the code given below :
Answer (b) & explanation
Only statement 3 is the reason (b). Step 1: the passage says world food supply matters because "the capabilities of individual countries to generate uninterrupted chain of food supplies have come under strain". That is statement 3, the limit on steady supply. Step 2: population overgrowth (1) is not stated as the reason. Step 3: a sharp fall in food-growing area (2) is also not stated. So options (a), (c) and (d) fail.
Tip: avoid choosing an option just because it is true in real life. Population growth does raise food demand, but the question asks what the passage gives as the reason. Stay inside the passage.
Answer as per the official UPSC answer key.
Four-digit numbers are to be formed using the digits 1, 2, 3 and 4; and none of these four digits are repeated in any manner. Further,
- 1. 2 and 3 are not to immediately follow each other
- 2. 1 is not to be immediately followed by 3
- 3. 4 is not to appear at the last place
- 4. 1 is not to appear at the first place
How many different numbers can be formed ?
Answer (a) & explanation
Six numbers can be formed (a). Step 1: the rules are: 2 and 3 are not next to each other, 1 is not directly before 3, 4 is not last, and 1 is not first. So each number starts with 2, 3 or 4. Step 2: test each arrangement. Numbers starting with 2: 2143, 2431. Starting with 3: 3142, 3412, 3421. Starting with 4: 4312. Step 3: every other order breaks a rule, for example 2134 ends in 4, and 4213 has 1 before 3. That is 6 numbers. Options (b), (c) and (d) do not fit.
Tip: when there are only 24 orders, list them in a fixed order by first digit. A neat list stops you missing or repeating any.
Answer as per the official UPSC answer key.
A cylindrical overhead tank of radius 2 m and height 7 m is to be filled from an underground tank of size 5·5 m × 4 m × 6 m. How much portion of the underground tank is still filled with water after filling the overhead tank completely?
Answer (a) & explanation
One-third of the underground tank is still full (a). Step 1: the overhead tank is a cylinder. Volume = πr²h = 22/7 × 2 × 2 × 7 = 88 m³. Step 2: the underground tank is a cuboid. Volume = 5.5 × 4 × 6 = 132 m³. Step 3: water left = 132 − 88 = 44 m³. As a fraction: 44 ÷ 132 = 1/3. Option (b), 1/2, and options (c) and (d) do not fit. Here π = 22/7 cancels neatly with the 7 m height.
Tip: when the height is 7 or a multiple of 7, use 22/7 for π. It makes the numbers come out whole.
88/132 = 2/3 is what was taken out. The question asks what is left.
Answer as per the official UPSC answer key.
In a class of 60 students, where the number of girls is twice that of boys, Kamal, a boy, ranked seventeenth from the top. If there are 9 girls ahead of Kamal, the number of boys in rank after him is :
Answer (b) & explanation
12 boys rank after Kamal (b). Step 1: girls are twice the boys, and there are 60 students. So boys = 60 ÷ 3 = 20, girls = 40. Step 2: Kamal is 17th, so 16 students are ahead of him. Nine of them are girls, so 16 − 9 = 7 are boys. Step 3: boys after Kamal = 20 − 7 − 1 (Kamal himself) = 12. Option (a), 13, forgets to remove Kamal. Option (c), 7, is the boys ahead of him. Option (d), 3, does not fit.
Tip: in rank questions, always remember to count or remove the person himself. That is the most common mistake.
Answer as per the official UPSC answer key.
A and B walk around a circular park. They start at 8 a.m. from the same point in the opposite directions. A and B walk at a speed of 2 rounds per hour and 3 rounds per hour respectively. How many times shall they cross each other after 8.00 a.m. and before 9.30 a.m.?
Answer (a) & explanation
They cross each other 7 times (a). Step 1: they walk in opposite directions, so their speeds add: 2 + 3 = 5 rounds per hour. Together they cover one full round every 60 ÷ 5 = 12 minutes. So they meet every 12 minutes. Step 2: from 8:00 to 9:30 is 90 minutes. They meet at 8:12, 8:24, 8:36, 8:48, 9:00, 9:12 and 9:24. Step 3: the next meeting is at 9:36, which is too late. So they cross 7 times. Option (b), 6, misses one. Option (c), 5, uses 1 hour. Option (d), 8, counts 9:36.
Tip: in circular tracks, opposite directions add speeds and the same direction subtracts them.
Answer as per the official UPSC answer key.
W can do 25% of a work in 30 days, X can do 1/4 of the work in 10 days, Y can do 40% of the work in 40 days and Z can do 1/3 of the work in 13 days. Who will complete the work first?
Answer (d) & explanation
Z will finish first (d). Step 1: work out each person's time for the whole job. W does 25% in 30 days, so the whole job takes 4 × 30 = 120 days. X does 1/4 in 10 days, so 40 days. Step 2: Y does 40% in 40 days, so 40 ÷ 0.4 = 100 days. Z does 1/3 in 13 days, so 3 × 13 = 39 days. Step 3: the shortest time is Z's 39 days. Option (b), X, is close at 40 days but slower. Options (a) W and (c) Y are much slower.
Tip: put everyone on the same base, the full job, before comparing. Close numbers like 39 and 40 are the setter's trap.
X looks fastest at a glance. Z's 1/3 in 13 days is just quicker.
Answer as per the official UPSC answer key.
The average monthly income of a person in a certain family of 5 is Rs. 10,000. What will be the average monthly income of a person in the same family if the income of one person increased by Rs. 1,20,000 per year?
Answer (a) & explanation
The new average is Rs 12,000 (a). Step 1: the family's total monthly income = 5 × 10,000 = Rs 50,000. Step 2: one person's income rises by Rs 1,20,000 a year. That is 1,20,000 ÷ 12 = Rs 10,000 a month. Step 3: new total = 50,000 + 10,000 = 60,000. New average = 60,000 ÷ 5 = Rs 12,000. Option (d), Rs 34,000, wrongly adds the yearly figure to the monthly one. Options (b) and (c) do not fit.
Tip: watch the time units. Convert yearly to monthly (divide by 12) before mixing figures. An increase shared over 5 people raises the average by one-fifth of it.
Rs. 34,000 adds the yearly figure to a monthly average.
Answer as per the official UPSC answer key.
In a race, a competitor has to collect 6 apples which are kept in a straight line on a track and a bucket is placed at the beginning of the track which is a starting point. The condition is that the competitor can pick only one apple at a time, run back with it and drop it in the bucket. If he has to drop all the apples in the bucket, how much total distance he has to run if the bucket is 5 meters from the first apple and all other apples are placed 3 meters apart?
Answer (d) & explanation
He runs 150 m in total (d). Step 1: the first apple is 5 m from the bucket, and each next one is 3 m further. So the apples are at 5, 8, 11, 14, 17 and 20 m. Step 2: add them: 5 + 8 + 11 + 14 + 17 + 20 = 75 m. Step 3: for each apple, he runs out and back, so each trip is doubled. Total = 2 × 75 = 150 m. Option (c), 75 m, is the trap: it counts only one way. Options (a) and (b) do not fit.
Tip: in "pick and return" problems, every trip is a round trip. For evenly spaced items, the sum = number × (first + last) ÷ 2 = 6 × 25 ÷ 2 = 75.
75 m counts only one way.
Answer as per the official UPSC answer key.
A round archery target of diameter 1 m is marked with four scoring regions from the centre outwards as red, blue, yellow and white. The radius of the red band is 0.20 m. The width of all the remaining bands is equal. If archers throw arrows towards the target, what is the probability that the arrows fall in the red region of the archery target ?
Answer (c) & explanation
The probability of hitting red is 0.16 (c). Step 1: the target's diameter is 1 m, so its radius is 0.5 m. The red circle's radius is 0.2 m. Step 2: probability = red area ÷ whole area = π × 0.2² ÷ π × 0.5². The π cancels. Step 3: = (0.2 ÷ 0.5)² = 0.4² = 0.16. Option (a), 0.40, compares radii instead of areas. Option (b), 0.20, compares the red radius with the diameter. Option (d), 0.04, is just 0.2².
Tip: area grows with the square of the radius. When comparing circles, square the ratio of their radii. The widths of the other bands do not matter here.
the areas go with the square of the radius, so 0.2/0.5 = 0.4 is the trap.
Answer as per the official UPSC answer key.
A person allows a 10% discount for cash payment from the marked price of a toy and still he makes a 10% gain. What is the cost price of the toy which is marked Rs. 770?
Answer (c) & explanation
The cost price is Rs 630 (c). Step 1: the marked price is Rs 770. A 10% discount gives a selling price of 90% of 770 = Rs 693. Step 2: he still makes a 10% profit, so 693 is 110% of the cost price. Step 3: cost price = 693 ÷ 1.1 = Rs 630. Check: 630 + 10% = 693. Option (a), Rs 610, and options (b) and (d) do not fit. A common mistake is to think a 10% discount and a 10% gain cancel out, giving 770.
Tip: discount is always on the marked price, and profit is always on the cost price. Keep the two bases separate.
Answer as per the official UPSC answer key.
All years by topic
Every question from 2011 to 2026, grouped by syllabus topic, with year-wise trends.