CSAT (Paper II): previous-year questions
1280 real UPSC Prelims questions (2011–2026) with the official answer and a clear explanation. 400 of them came in the last five papers.
How often UPSC asks this
Questions per year, counted from the official papers.
Subtopics
Arrangements, ranking, ordering and puzzles
142 questions
Clocks and calendars
5 questions
Coding-decoding, series, patterns, cubes, dice and visual reasoning
110 questions
Communication, interpersonal skills and decision-making
10 questions
Counting, permutations, combinations and probability
1 questions
Directions, blood relations and Venn diagrams
60 questions
General English: grammar, vocabulary and comprehension
20 questions
General Hindi: grammar, vocabulary, dialects and comprehension
25 questions
Geometry and mensuration
26 questions
Number system and basic algebra (divisibility, HCF/LCM, remainders, digits, equations)
196 questions
Percentages, profit and loss, discount, simple and compound interest
47 questions
Ratio, proportion, averages, mixtures and alligation
47 questions
Syllogisms, statements and conclusions, assumptions and arguments
89 questions
Time and work; pipes and cisterns
2 questions
Time, speed and distance; trains, boats and streams; races
48 questions
Attempt the questions
Newest papers first. Tap an option; the answer and the reason appear instantly.
Read the passage
India’s economic footprint, given its population, still remains small compared to the US, the European Union or China. It has much to learn from other economies, yet must implement solutions that fit its unique circumstances. India especially needs an effective long-term regulatory system based on collaboration rather than the current top-down approach. Regulations seek desirable outcomes yet are repeatedly used as political tools to push one agenda or another. Often, regulations fail to consider impacts on jobs and economic growth — or less restrictive alternatives. Regulations may be used to protect local markets at the expense of more widely shared prosperity in the future. Additionally, regulations inevitably result in numerous unintended consequences. In today’s hyper competitive global economy, regulations need to be viewed as “weapons” that seek cost-justified social and environmental benefits while improving the economic well-being of most citizens.
Which one of the following is the most logical, rational and crucial inference that can be derived from the above passage ?
Answer (b) & explanation
The inference is that India must use regulations strategically in a competitive global economy (b). Step 1: the passage says regulations "need to be viewed as 'weapons'" that must be cost-justified in a "hyper competitive global economy". That means using them strategically. That is (b). Step 2: option (d) makes jobs and growth the dominant concern. The passage also values social and environmental gains, so (d) overstates. Step 3: option (a) links regulation to the size of the economy, which the passage does not say. Option (c) claims India's rules block integration, also unsupported.
Tip: a key metaphor ("weapons") often carries the main message. Choose the option closest to it.
Answer as per the official UPSC answer key.
Read the passage
Around 56 million years ago, the Atlantic Ocean had not fully opened and animals, perhaps including our primate ancestors, could walk from Asia to North America through Europe and across Greenland. Earth was warmer than it is today, but as the Palaeocene epoch gave way to Eocene, it was about to get much warmer still — rapidly and radically. The cause was a massive geologically sudden release of carbon. During this period called Palaeocene-Eocene Thermal Maximum or PETM, the carbon injected into the atmosphere was roughly the amount that would be injected today if humans burned all the Earth’s reserves of coal, oil and natural gas. The PETM lasted for about 1,50,000 years, until the excess carbon was reabsorbed. It brought on drought, floods, insect plagues and a few extinctions. Life on Earth survived — indeed, it prospered — but it was drastically different.
Based on the above passage, the following assumptions have been made :
- 1. Global warming has a bearing on the planet’s biological evolution.
- 2. Separation of land masses causes the release of huge quantities of carbon into the atmosphere.
- 3. Increased warming of Earth’s atmosphere can change the composition of its flora and fauna.
- 4. The present man-made global warming will finally lead to conditions similar to those which happened 56 million years ago.
Which of the assumptions given above are valid ?
Answer (c) & explanation
Assumptions 1 and 3 are valid (c). Step 1: the passage says that after the warming event 56 million years ago (the PETM), life "prospered, but it was drastically different". So warming affects evolution (1) and changes the mix of plants and animals (3). Step 2: assumption 2 says separating land masses released the carbon. The passage gives no cause for the carbon release, so 2 fails. Step 3: assumption 4 predicts that today's warming will lead to the same conditions. The passage makes no forecast, so 4 fails. Options (a), (b) and (d) fail.
Tip: a passage about the past rarely supports a firm prediction about the future. Reject "will finally lead to" type claims.
Answer as per the official UPSC answer key.
The average marks of 100 students are given to be 40. It was found later that marks of one student were 53 which were misread as 83. The corrected mean marks are
Answer (b) & explanation
The corrected mean is 39·7 (b). Step 1: total marks as first counted = 100 × 40 = 4000. Step 2: one mark was read as 83 instead of 53, which is 30 too high. Correct total = 4000 − 30 = 3970. Step 3: correct average = 3970 ÷ 100 = 39·7. Option (d), 40·3, adds the 30 instead of subtracting it. Option (c) ignores the error. Option (a) takes off the whole 1 mark.
Tip: shortcut: the average changes by (error ÷ number of items). Here 30 ÷ 100 = 0·3 too high, so the true average is 40 − 0·3 = 39·7.
Answer as per the official UPSC answer key.
Each face of a cube can be painted in black or white colours. In how many different ways can the cube be painted ?
Answer (b) & explanation
A cube can be painted in 10 different ways (b). Step 1: count by the number of black faces. 0 black: 1 way. 1 black: 1 way (any face looks the same after turning). Step 2: 2 black: 2 ways, either next to each other or opposite. 3 black: 2 ways, either all three meeting at a corner, or in a row like a band. Step 3: 4 black is the same as 2 white: 2 ways. 5 black: 1 way. 6 black: 1 way. Total = 1 + 1 + 2 + 2 + 2 + 1 + 1 = 10. Options (a), (c) and (d) miscount.
Tip: two cube colourings are the same if one can be turned to look like the other. Count patterns, not face labels.
a cube can be turned, so two paintings that match after turning are the same.
Answer as per the official UPSC answer key.
Rakesh and Rajesh together bought 10 balls and 10 rackets. Rakesh spent ₹ 1300 and Rajesh spent ₹ 1500. If each racket costs three times a ball does, then what is the price of a racket?
Answer (c) & explanation
A racket costs ₹ 210 (c). Step 1: together they spent 1300 + 1500 = ₹ 2800 on 10 balls and 10 rackets. Step 2: let a ball cost b. A racket costs 3b. So 10b + 10 × 3b = 40b = 2800, and b = ₹ 70. Step 3: a racket = 3 × 70 = ₹ 210. Option (a), ₹ 70, is the price of a ball. Options (b) and (d) do not fit. How the cost was split between Rakesh and Rajesh does not matter.
Tip: CSAT often adds extra data to confuse you. Here the separate spends of ₹ 1300 and ₹ 1500 are not needed; only the total matters.
₹ 70 is the ball, not the racket.
Answer as per the official UPSC answer key.
What is X in the sequence
4, 196, 16, 144, 36, 100, 64, X?
Answer (b) & explanation
X is 64 (b). Step 1: split the series into two. Odd places: 4, 16, 36, 64 = 2², 4², 6², 8². Step 2: even places: 196, 144, 100 = 14², 12², 10². They fall by 2 each time. Step 3: X is in an even place, so X = 8² = 64. Option (d), 256, continues the odd-place series (16²) by mistake. Options (a) and (c) do not fit.
Tip: when a series jumps up and down, it is often two series mixed together. Separate the odd and even places. Knowing squares up to 25² and cubes up to 15³ makes such questions quick.
Answer as per the official UPSC answer key.
P, Q and R are three towns. The distance between P and Q is 60 km, whereas the distance between P and R is 80 km. Q is in the West of P and R is in the South of P. What is the distance between Q and R ?
Answer (d) & explanation
The distance between Q and R is 100 km (d). Step 1: Q is west of P and R is south of P. West and south are at right angles, so P is the right-angle corner of a triangle. Step 2: by Pythagoras, QR² = 60² + 80² = 3600 + 6400 = 10,000. Step 3: so QR = √10,000 = 100 km. Option (a), 140 km, simply adds 60 and 80, which would be true only if you travelled via P. Options (b) and (c) do not fit.
Tip: 60-80-100 is the 3-4-5 triangle multiplied by 20. Spotting such triples saves calculation. Direction questions with north-south and east-west legs almost always use Pythagoras.
Answer as per the official UPSC answer key.
Read the passage
India’s economic footprint, given its population, still remains small compared to the US, the European Union or China. It has much to learn from other economies, yet must implement solutions that fit its unique circumstances. India especially needs an effective long-term regulatory system based on collaboration rather than the current top-down approach. Regulations seek desirable outcomes yet are repeatedly used as political tools to push one agenda or another. Often, regulations fail to consider impacts on jobs and economic growth — or less restrictive alternatives. Regulations may be used to protect local markets at the expense of more widely shared prosperity in the future. Additionally, regulations inevitably result in numerous unintended consequences. In today’s hyper competitive global economy, regulations need to be viewed as “weapons” that seek cost-justified social and environmental benefits while improving the economic well-being of most citizens.
On the basis of the above passage, the following assumptions have been made : In today’s global economy,
- 1. regulations are not effectively used to protect local markets.
- 2. social and environmental concerns are generally ignored by the governments across the world while implementing the regulations.
Which of the above assumptions is/are valid ?
Answer (d) & explanation
Neither assumption is valid (d). Step 1: the passage says regulations "may be used to protect local markets". Assumption 1 says they are not effectively used for this. That is the opposite of what the passage suggests, so 1 fails. Step 2: assumption 2 says governments generally ignore social and environmental concerns. The passage never says this. Step 3: so options (a), (b) and (c) fail.
Tip: an assumption must agree with the passage, not contradict it. Also beware of sweeping words like "generally ignored by governments across the world"; such broad claims need clear support, which passages rarely give.
Answer as per the official UPSC answer key.
The number of times the digit 5 will appear while writing the integers from 1 to 1000 is
Answer (c) & explanation
The digit 5 appears 300 times (c). Step 1: write the numbers 000 to 999 as three-digit strings. There are 1000 strings with 3 places each, so 3000 digits in all. Step 2: each digit 0 to 9 appears equally often: 3000 ÷ 10 = 300. Leading zeros do not affect the count of 5s. Step 3: the number 1000 has no 5, so the answer stays 300. Check another way: 5 appears 100 times in the units place, 100 in the tens and 100 in the hundreds. Options (a), (b) and (d) are wrong.
Tip: from 1 to 999, every non-zero digit appears 300 times. Counting place by place (units, tens, hundreds) is the safest method.
269 and 271 come from counting only the numbers that contain a 5. A number like 55 has two 5s.
Answer as per the official UPSC answer key.
Read the passage
What stands in the way of the widespread and careful adoption of ‘Genetic Modification (GM)’ technology is an ‘Intellectual Property Rights’ regime that seeks to create private monopolies for such technologies. If GM technology is largely corporate driven, it seeks to maximize profits and that too in the short run. That is why corporations make major investments for herbicide-tolerant and pest-resistant crops. Such properties have only a short window, as soon enough, pests and weeds will evolve to overcome such resistance. This suits the corporations. The National Farmers Commission pointed out that priority must be given in genetic modification to the incorporation of genes that can help impart resistance to drought, salinity and other stresses.
Which one of the following is the most logical, rational and crucial message conveyed by the above passage ?
Answer (a) & explanation
The message is that public research institutions should lead GM technology and set its agenda (a). Step 1: the passage says corporate GM research chases short-term profit. It ignores farmers' real needs, like crops that resist drought or salinity. So public bodies should set the agenda. That is (a). Step 2: option (b), abolishing intellectual property rights, is extreme. Option (c), banning private firms from seed business, is also extreme. Step 3: option (d) says India should not grow GM crops at all. The passage wants GM used better, not dropped.
Tip: if a passage criticises who controls a technology, the answer usually shifts control, not bans the technology. In India, ICAR and state agricultural universities do such public research.
Answer as per the official UPSC answer key.
How many triplets (x, y, z) satisfy the equation x + y + z = 6, where x, y and z are natural numbers ?
Answer (d) & explanation
10 triplets satisfy the equation (d). Step 1: natural numbers start at 1, so zero is not allowed. List the sets of three numbers that add to 6: 1, 1, 4; 1, 2, 3; 2, 2, 2. Step 2: count the orders. 1, 1, 4 can be arranged in 3 ways. 1, 2, 3 in 6 ways. 2, 2, 2 in 1 way. Step 3: total = 3 + 6 + 1 = 10. Option (b), 5, and option (c), 9, miss some orders. Option (a) counts only the sets.
Tip: formula: the number of ways to write n as a sum of k natural numbers (order counts) is (n − 1)C(k − 1). Here 5C2 = 10.
Answer as per the official UPSC answer key.
In a conference, out of a total 100 participants, 70 are Indians. If 60 of the total participants are vegetarian, then which of the following statements is/are correct ?
- 1. At least 30 Indian participants are vegetarian.
- 2. At least 10 Indian participants are non-vegetarian.
Select the correct answer using the code given below :
Answer (c) & explanation
Both statements are correct (c). Step 1: the smallest possible overlap of two groups = group A + group B − total. Step 2: Indians and vegetarians: 70 + 60 − 100 = 30. So at least 30 Indians are vegetarian. Statement 1 holds. Step 3: there are 100 − 60 = 40 non-vegetarians. Indians and non-vegetarians: 70 + 40 − 100 = 10. So at least 10 Indians are non-vegetarian. Statement 2 holds. Options (a), (b) and (d) fail.
Tip: remember minimum overlap = A + B − total. Picture it: even if all 30 non-Indians are vegetarian, 30 more vegetarians must be Indian.
Answer as per the official UPSC answer key.
In a group of 15 people, 7 can read French, 8 can read English while 3 of them can read neither of these two languages. The number of people who can read exactly one language is
Answer (b) & explanation
9 people can read exactly one language (b). Step 1: 3 read neither, so 15 − 3 = 12 read at least one. Step 2: both = 7 + 8 − 12 = 3. Step 3: exactly one = those who read at least one − those who read both = 12 − 3 = 9. Check: French only = 7 − 3 = 4; English only = 8 − 3 = 5; 4 + 5 = 9. Option (a), 10, forgets to subtract correctly. Option (c), 5, and (d), 4, give only one language's "only" group.
Tip: "exactly one" = (A only) + (B only). Always remove the "neither" group before using the overlap formula.
Answer as per the official UPSC answer key.
All members of a club went to Mumbai and stayed in a hotel. On the first day, 80% went for shopping and 50% went for sightseeing, whereas 10% took rest in the hotel. Which of the following conclusion(s) can be drawn from the above data ?
- 1. 40% members went for shopping as well as sightseeing.
- 2. 20% members went for only shopping.
Select the correct answer using the code given below :
Answer (a) & explanation
Only conclusion 1 can be drawn (a). Step 1: 10% stayed in the hotel, so 90% went out. Step 2: both shopping and sightseeing = 80 + 50 − 90 = 40%. So conclusion 1 is correct. Step 3: only shopping = all shoppers − those who did both = 80 − 40 = 40%, not 20%. So conclusion 2 is wrong. Options (b), (c) and (d) fail.
Tip: always remove the "neither" group first. Then use: both = A + B − (those in at least one). A quick two-circle diagram makes "only A" and "both" easy to read off. Option (b) traps those who subtract 80 from 100 to get 20%.
Answer as per the official UPSC answer key.
Read the passage
In a study, scientists compared the microbiomes of poorly nourished and well nourished infants and young children. Gut microbes were isolated from faecal samples of malnourished and healthy children. The microbiome was “immature” and less diverse in malnourished children compared to the better developed “mature” microbiome found in healthy children of the same age. According to some studies, the chemical composition of mother’s milk has shown the presence of a modified sugar (sialylated oligosaccharides). This is not utilized by the baby for its own nutrition. However, the bacteria constituting the infant’s microbiome thrive on this sugar which serves as their food. Malnourished mothers have low levels of this sugar in their milk. Consequently, the microbiomes of their infants fail to mature. That in turn, leads to malnourished babies.
Which one of the following is the most logical, rational and crucial inference that can be derived from the above passage ?
Answer (d) & explanation
The inference is that research on gut bacteria and nutrition has policy implications (d). Step 1: the study links mothers' milk, gut bacteria and malnutrition in babies. Such findings can shape nutrition policy. That is (d). Step 2: options (b) and (c) suggest specific treatments: putting mature microbiomes into babies' guts, or replacing mother's milk with fortified dairy milk. The passage never tests these, and (c) even goes against breastfeeding. Step 3: option (a) says the condition cannot be treated; that is defeatist and not stated.
Tip: when a passage reports early research, the safe inference is that it "has implications". Specific cures go beyond the evidence.
Answer as per the official UPSC answer key.
A solid cube is painted yellow, blue and black such that opposite faces are of same colour. The cube is then cut into 36 cubes of two different sizes such that 32 cubes are small and the other four cubes are big. None of the faces of the bigger cubes is painted blue. How many cubes have only one face painted ?
Answer (c) & explanation
1. Volume check: 4 big cubes of side 2 and 32 small cubes of side 1 give 32 + 32 = 64, so the cube is 4 × 4 × 4.
2. The big cubes avoid both blue faces, so they fill the middle two layers between the blue faces. The two blue layers (16 small cubes each) hold the 32 small cubes.
3. In each blue layer only the inner 2 × 2 = 4 cubes have just the blue face painted. The big cubes each touch two side faces. Total = 4 + 4 = 8.
Answer as per the official UPSC answer key.
Read the passage
What stands in the way of the widespread and careful adoption of ‘Genetic Modification (GM)’ technology is an ‘Intellectual Property Rights’ regime that seeks to create private monopolies for such technologies. If GM technology is largely corporate driven, it seeks to maximize profits and that too in the short run. That is why corporations make major investments for herbicide-tolerant and pest-resistant crops. Such properties have only a short window, as soon enough, pests and weeds will evolve to overcome such resistance. This suits the corporations. The National Farmers Commission pointed out that priority must be given in genetic modification to the incorporation of genes that can help impart resistance to drought, salinity and other stresses.
On the basis of the above passage, the following assumptions have been made :
- 1. The issue of effects of natural calamities on agriculture is not given due consideration by GM technology companies.
- 2. In the long run, GM technology will not be able to solve agricultural problems arising due to global warming.
Which of the above assumptions is/are valid ?
Answer (a) & explanation
Only assumption 1 is valid (a). Step 1: the passage says GM companies invest in herbicide and pest traits. Traits for drought and salinity, which matter for natural calamities, are left for a Commission to urge. So companies neglect this issue. Assumption 1 holds. Step 2: assumption 2 says GM will not solve climate-related farm problems in the long run. But the passage wants GM to be used for these stresses, so it believes GM can help. Assumption 2 contradicts the passage. Step 3: options (b), (c) and (d) fail.
Tip: an assumption that goes against the author's hope cannot be valid. Check whether the passage sees a tool as useless or just badly used.
Answer as per the official UPSC answer key.
If $ means 'divided by'; @ means 'multiplied by'; # means 'minus', then the value of 10#5@1$5 is
Answer (d) & explanation
The value is 9 (d). Step 1: replace the symbols: # is minus, @ is times, $ is divided by. So 10#5@1$5 becomes 10 − 5 × 1 ÷ 5. Step 2: by BODMAS, do multiplication and division first, left to right: 5 × 1 = 5, then 5 ÷ 5 = 1. Step 3: then subtract: 10 − 1 = 9. Option (b), 1, works left to right without BODMAS: (10 − 5) × 1 ÷ 5 = 1. Options (a) and (c) are also wrong.
Tip: after swapping symbols, always apply BODMAS: Brackets, Orders, Division and Multiplication, then Addition and Subtraction. The trap answer usually comes from working left to right.
Answer as per the official UPSC answer key.
Read the passage
Low-end IoT (Internet of Things) devices are cheap commodity items : addressing security would add to the cost. This class of items is proliferating with new applications; many home appliances, thermostats, security and monitoring devices and personal convenience devices are part of the IoT. So are fitness trackers, certain medical implants and computer-like devices in automobiles. The IoT is expected to expand exponentially — but new security challenges are daunting.
Which one of the following statements is the most logical and rational inference that can be made from the above passage ?
Answer (d) & explanation
The inference is that some IoT devices pose a huge threat to internet security (d). Step 1: the passage says cheap IoT (Internet of Things) devices skip security to save cost, yet they spread fast. It adds that "security challenges are daunting". That is (d). Step 2: options (a) and (b) bring in India, which the passage never mentions. Step 3: option (c), comfort from cheap devices, misses the main point, which is the risk.
Tip: IoT means everyday devices linked to the internet, like smart cameras, bulbs and watches. Weakly protected ones can be hijacked in large numbers to attack websites. Pick the option that names the passage's central concern.
Answer as per the official UPSC answer key.
A printer numbers the pages of a book starting with 1 and uses 3089 digits in all. How many pages does the book have?
Answer (c) & explanation
The book has 1049 pages (c). Step 1: count digits used. Pages 1 to 9: 9 digits. Pages 10 to 99: 90 pages × 2 = 180. Pages 100 to 999: 900 × 3 = 2700. Total so far = 2889. Step 2: digits left = 3089 − 2889 = 200. Each page from 1000 on uses 4 digits, so 200 ÷ 4 = 50 pages. Step 3: last page = 999 + 50 = 1049. Option (d), 1050, adds one too many. Options (a) and (b) undercount.
Tip: remember the block totals: 9, 189 (to 99) and 2889 (to 999). Then divide the remainder by the digits per page.
Answer as per the official UPSC answer key.