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.
What is the remainder when 51 × 27 × 35 × 62 × 75 is divided by 100?
Answer (a) & explanation
The remainder is 50 (a). Step 1: the remainder on dividing by 100 is just the last two digits. So keep only the last two digits at each step. Step 2: 35 × 62 = 2170 → 70. 70 × 75 = 5250 → 50. 50 × 27 = 1350 → 50. 50 × 51 = 2550 → 50. Step 3: the remainder is 50. Option (b), 25, and option (c), 5, come from multiplying only the 5-ending numbers. Option (d) fails.
Tip: an even number times a multiple of 25 gives a multiple of 50. Here 62 is even and 75 is a multiple of 25, and the other factors are odd, so the product ends in 50.
Answer as per the official UPSC answer key.
Read the passage
One of the biggest ironies around water is that it comes from rivers and other wetlands. Yet it is seen as divorced from them. While water is used as a resource, public policy does not always grasp that it is a part of the natural ecosystem. Efforts at engineering water systems are thus efforts at augmenting water supply rather than strengthening the capacities of ecological systems.
Which one of the following is the most logical and rational inference that can be made from the above passage?
Answer (c) & explanation
The inference is that wetlands must be seen as more than just open sources of water (c). Step 1: the passage says policy treats water as a resource "divorced" from wetlands. It ignores the wetland as a living ecosystem. So wetlands should be valued for more than water. That is (c). Step 2: option (b) asks to expand engineered water systems. That repeats the very approach the passage criticises. Step 3: option (a), the Ramsar Convention, is outside knowledge not in the passage. Option (d), charging for water, is not discussed.
Tip: avoid options that rely on facts the passage never gives, even if true. India has 90+ Ramsar sites, but that does not make (a) the inference here.
Answer as per the official UPSC answer key.
A is 16th from the left end in a row of boys and V is 18th from the right end. G is 11th from A towards the right and 3rd from V towards the right end. How many boys are there in the row?
Answer (b) & explanation
There are 41 boys in the row (b). Step 1: A is 16th from the left. G is 11 places to A's right, so G is 16 + 11 = 27th from the left. Step 2: G is 3rd from V towards the right, so V is 3 places to G's left: 24th from the left. Step 3: V is also 18th from the right. Total = 24 + 18 − 1 = 41. We subtract 1 because V is counted twice. Option (c), 42, forgets to subtract 1. Options (a) and (d) fail.
Tip: total in a row = position from left + position from right − 1. Fix one person's position from both ends to use this formula.
Answer as per the official UPSC answer key.
How many different 5-letter words (with or without meaning) can be constructed using all the letters of the word 'DELHI' so that each word has to start with D and end with I?
Answer (d) & explanation
6 such words can be made (d). Step 1: the word must start with D and end with I. So the first and last letters are fixed. Step 2: the middle three places are filled by E, L and H. Step 3: three letters can be arranged in 3 × 2 × 1 = 6 ways: ELH, EHL, LEH, LHE, HEL, HLE. Option (a), 24, fixes only one end (4! = 24). Options (b) and (c) do not follow any rule.
Tip: fix the letters whose places are given, then arrange the rest. n different letters can be arranged in n! ways. 3! = 6, 4! = 24, 5! = 120.
Answer as per the official UPSC answer key.
One page is torn from a booklet whose pages are numbered in the usual manner starting from the first page as 1. The sum of the numbers on the remaining pages is 195. The torn page contains which of the following numbers?
Answer (b) & explanation
The torn page has 7 and 8 (b). Step 1: find the total before tearing. 1 + 2 + … + 20 = 20 × 21 ÷ 2 = 210. 1 to 19 gives only 190, which is less than 195, so the booklet had 20 pages. Step 2: missing sum = 210 − 195 = 15. Step 3: a torn leaf has two consecutive numbers that add to 15: 7 + 8. Option (a), 5 + 6 = 11. Option (c), 9 + 10 = 19. Option (d), 11 + 12 = 23. None of these is 15.
Tip: use n(n + 1) ÷ 2 for the sum of 1 to n. Find the smallest total just above the given sum; the difference is the torn page.
Answer as per the official UPSC answer key.
Read the passage
Economic liberalization in India was shaped largely by the economic problems of the government than by the economic priorities of the people or by the long-term development objectives. Thus, there were limitations in conception and design which have been subsequently validated by experience. Jobless growth, persistent poverty and rising inequality have mounted as problems since economic liberalization began. And all these years later, four quiet crises confront the economy; agriculture, infrastructure, industrialization and education as constraints on the country’s future prospects. These problems must be resolved if economic growth has to be sustained and transformed into meaningful development.
With reference to the above passage, the following assumptions have been made :
- 1. India’s economy needs to be greatly integrated with global economy so as to create large number of jobs and to sustain its growth momentum.
- 2. Economic liberalization would cause large economic growth which would reduce poverty and create sufficient employment in the long run.
Which of the above assumptions is/are valid?
Answer (d) & explanation
Neither assumption is valid (d). Step 1: the passage blames liberalisation for "jobless growth, persistent poverty and rising inequality". Step 2: assumption 1 says India needs more integration with the global economy to create jobs. That praises integration, against the passage's tone. Step 3: assumption 2 says liberalisation will cut poverty and create jobs in the long run. That also praises it. Both go against the passage. So options (a), (b) and (c) fail.
Tip: check the author's attitude. If the passage is critical of a policy, statements praising that policy cannot be its assumptions.
Answer as per the official UPSC answer key.
If 1 litre of water weighs 1 kg, then how many cubic millimetres of water will weigh 0·1 gm?
Answer (c) & explanation
100 cubic millimetres of water weigh 0·1 gm (c). Step 1: 1 litre weighs 1 kg, so 1 ml weighs 1 g. And 1 ml = 1 cm³. Step 2: 1 cm = 10 mm, so 1 cm³ = 10 × 10 × 10 = 1000 mm³. So 1 g of water = 1000 mm³. Step 3: 0·1 g = 0·1 × 1000 = 100 mm³. Option (d), 1000, is the volume for 1 g. Options (a) and (b) fail.
Tip: water facts to remember: 1 ml = 1 cm³ = 1 g; 1 litre = 1000 cm³ = 1 kg. When converting cubic units, cube the length factor: (10)³ = 1000.
Answer as per the official UPSC answer key.
Read the passage
Our urban bodies cannot possibly ensure sustainable delivery of water in our cities unless financing mechanisms are put in place. Water delivery requires heavy investment in collecting it from a natural source, treating it to make it potable, and laying a distribution network of pipes for delivery to the users. It also requires investments in sewerage infrastructure and sewage treatment plants so that the sewers can carry the wastewater to these plants to ensure that no untreated sewage is discharged back into natural water bodies. If our cities were rich enough to meet the entire cost, water could be delivered free. They are not.
With reference to the above passage, the following assumptions have been made :
- 1. Rich cities only can ensure sustainable delivery of water.
- 2. Sustainable delivery of water in cities means much more than supplying water to households.
Which of the above assumptions is/are valid?
Answer (b) & explanation
Only assumption 2 is valid (b). Step 1: the passage says water delivery includes treatment, pipes, sewers and sewage plants. So sustainable delivery means much more than supplying water to homes (2). Step 2: assumption 1 says only rich cities can do this. But the passage says poorer cities can also deliver with "financing mechanisms". So 1 fails. Step 3: so options (a), (c) and (d) fail.
Tip: "only" claims fail if the passage shows another way. India's AMRUT 2.0 mission funds water supply and sewerage in cities that cannot pay alone.
Answer as per the official UPSC answer key.
A sum of ₹ 2,500 is distributed among X, Y and Z in the ratio 1/2 : 3/4 : 5/6. What is the difference between the maximum share and the minimum share?
Answer (c) & explanation
The difference is ₹ 400 (c). Step 1: clear the fractions by multiplying each by 12 (the LCM of 2, 4 and 6): ½ × 12 = 6, ¾ × 12 = 9, ⅚ × 12 = 10. So the ratio is 6 : 9 : 10. Step 2: total parts = 25. One part = 2500 ÷ 25 = ₹ 100. Step 3: maximum − minimum = (10 − 6) × 100 = ₹ 400. So X gets ₹ 600, Y ₹ 900 and Z ₹ 1000. Options (a), (b) and (d) do not fit.
Tip: to simplify a ratio of fractions, multiply all terms by the LCM of the denominators. Then share the total by parts.
Answer as per the official UPSC answer key.
Read the passage
Asset allocation is the most important investment decision we will ever make, and sadly, most of us do not give that decision the importance it deserves. We are adamant about seeking predictability with our future. We tend to think of investing in risky assets as extremely volatile and value eroding. We also dislike fluctuating returns and the loss of control of investment. We think our money is best left idle, unproductive but safe. There is no asset that is risk-free. We could lose our jobs, our homes can lose value, our banks can go bankrupt, our bonds can default, the government can collapse and companies we chose fondly may cease to exist. But we cannot live life assuming that all these extreme events are waiting to happen, and all at the same time. All these extreme forms of risks we know will not manifest at the same time.
Which one of the following statements best implies the suggestion given by the author of the passage?
Answer (a) & explanation
The author suggests spreading wealth across different assets to cut risk (a). Step 1: the passage says no asset is risk-free, but all risks "will not manifest at the same time". So holding many kinds of assets means losses in one are offset by gains in another. That is diversification, option (a). Step 2: option (d), investing is risky, just restates a fact; it is not a suggestion. Step 3: option (b) makes risk-taking a necessary part of personality, which overstates. Option (c), hiring an asset manager, is not mentioned.
Tip: "don't put all your eggs in one basket" is the core idea. When asked for a suggestion, pick an action that solves the problem the passage describes.
Answer as per the official UPSC answer key.
Three Statements S1, S2 and S3 are given below followed by a Question :
S1 : C is younger than D, but older than A and B.
S2 : D is the oldest.
S3 : A is older than B.
Question : Who among A, B, C and D is the youngest?
Which one of the following is correct in respect of the above Statements and the Question?
Answer (d) & explanation
S1 and S3 together are sufficient (d). Step 1: S1 says C is younger than D but older than A and B. So D and C are above A and B. The youngest is A or B. S1 alone is not enough. Step 2: S3 says A is older than B. Combined with S1, B is the youngest. Step 3: S2 (D is oldest) adds nothing new, since S1 already places D above C, A and B. So options (a), (b) and (c) fail.
Tip: in such questions, look for the statement that breaks the final tie. Here S1 narrows it to two people, and S3 decides between them.
Answer as per the official UPSC answer key.
A bottle contains 20 litres of liquid A. 4 litres of liquid A is taken out of it and replaced by same quantity of liquid B. Again 4 litres of the mixture is taken out and replaced by same quantity of liquid B. What is the ratio of quantity of liquid A to that of liquid B in the final mixture?
Answer (c) & explanation
The final ratio of A to B is 16 : 9 (c). Step 1: each round removes 4 of 20 litres, so it keeps 16/20 = 4/5 of liquid A. Step 2: after two rounds: A = 20 × (4/5) × (4/5) = 20 × 16/25 = 12·8 litres. Step 3: B = 20 − 12·8 = 7·2 litres. Ratio 12·8 : 7·2 = 128 : 72 = 16 : 9. Option (a), 4 : 1, is the ratio after only one round (16 : 4). Options (b) and (d) fail.
Tip: for repeated replacement, use: remaining = original × (1 − removed/total)ⁿ. This formula saves step-by-step work.
Answer as per the official UPSC answer key.
Consider the following arrangement that has some missing letters :
abab_b_bcb_dcdcded_d
The missing letters which complete the arrangement are
Answer (c) & explanation
The missing letters are a, c, c, e (c). Step 1: there are 20 letters. Split them into blocks of five: abab_ | b_bcb | _dcdc | ded_d. Step 2: each block alternates two letters: ababa, bcbcb, cdcdc, deded. Each new block moves one letter forward. Step 3: the blanks are a, c, c, e. That is option (c). Options (a), (b) and (d) break the alternating pattern.
Tip: count the total letters, then try equal blocks. A clean split (here 4 blocks of 5) usually shows the rule at once.
Answer as per the official UPSC answer key.
A shop owner offers the following discount options on an article to a customer :
- 1. Successive discounts of 10% and 20%, and then pay a service tax of 10%
- 2. Successive discounts of 20% and 10%, and then pay a service tax of 10%
- 3. Pay a service tax of 10% first, then successive discounts of 20% and 10%
Which one of the following is correct?
Answer (d) & explanation
All three options are equally good (d). Step 1: each option multiplies the price by the same three numbers: 0·9 (10% off), 0·8 (20% off) and 1·1 (10% tax). Step 2: multiplication can be done in any order: 0·9 × 0·8 × 1·1 = 0·8 × 0·9 × 1·1 = 1·1 × 0·8 × 0·9 = 0·792. Step 3: so the final price is the same in all three. Options (a), (b) and (c) fail.
Tip: successive percentage changes multiply, so their order never matters. Two successive discounts of 20% and 10% equal a single 28% discount, not 30%.
Answer as per the official UPSC answer key.
A vessel full of water weighs 40 kg. If it is one-third filled, its weight becomes 20 kg. What is the weight of the empty vessel?
Answer (a) & explanation
The empty vessel weighs 10 kg (a). Step 1: full weighs 40 kg; one-third full weighs 20 kg. Going from full to one-third full removes 2/3 of the water, and the weight drops by 40 − 20 = 20 kg. Step 2: so 2/3 of the water = 20 kg, and all the water = 30 kg. Step 3: vessel = 40 − 30 = 10 kg. Check: one-third water = 10 kg, plus vessel 10 kg = 20 kg. Options (b), (c) and (d) fail.
Tip: the difference between two states removes the vessel's weight. Use it to find the contents first, then subtract from the total.
Answer as per the official UPSC answer key.
Read the passage
In India, agriculture still engages about half of its workforce, and about 85 per cent of its farms are small and marginal. Compared to China and Vietnam, which have experienced fast structural and rural transformation, India’s story is of slow transformation. As a result, poverty reduction in India was at a much slower pace during 1988–2014, compared to China and Vietnam. India’s poverty reduction was slow during 1988–2005, but during 2005–2012, it accelerated dramatically—almost three times faster than during the earlier period. What did India do during this period? Research reveals that the relative price scenario changed significantly (by more than 50%) in favour of agriculture in the wake of rising global prices. This boosted private investments in agriculture by more than 50%. As a result, agri-GDP growth touched 4·1% during 2007–2012 as against 2·4% during 2002–2007. The net surplus of agri-trade touched $25 billion in 2013–2014; real farm wages rose by 7% per annum. All this led to unprecedented fall in poverty.
With reference to the above passage, the following assumptions have been made :
- 1. Structural and rural transformation is impossible when farms are mainly small and marginal.
- 2. A good price incentive can trigger investments in agriculture.
- 3. India needs to build value chains for high-value agri-products like livestock and horticulture.
- 4. Higher global prices of agricultural commodities are essential for India’s poverty reduction.
Which of the above assumptions are valid?
Answer (c) & explanation
Assumptions 2 and 3 are valid (c). Step 1: the passage says better relative prices raised private farm investment by over 50%. So a good price incentive triggers investment (2). Step 2: UPSC's key also reads into the price-led gains a need to build value chains for high-value products like livestock and horticulture (3). Step 3: assumption 1 says transformation is impossible with small farms; that is too strong. Assumption 4 says high global prices are essential for poverty reduction; also too strong. So options (a), (b) and (d) fail.
Tip: "impossible" and "essential" are absolute words. Unless the passage uses them, reject such statements.
Answer as per the official UPSC answer key.
For what value of n, the sum of digits in the number (10n + 1) is 2?
Answer (b) & explanation
The digit sum is 2 for any whole number n (b). Step 1: for n ≥ 1, 10ⁿ + 1 looks like 100…01: one 1, some zeros, then another 1. Digit sum = 2. Step 2: for n = 0, 10⁰ = 1, so 10⁰ + 1 = 2. Digit sum is also 2. Step 3: so it works for every whole number (0, 1, 2, …). Option (c) leaves out 0. Option (a) is too narrow. Option (d) fails because a fractional n, like 0·5, gives a non-whole number.
Tip: whole numbers include 0; natural (positive) numbers start at 1. CSAT often tests this difference, so always check n = 0 separately.
don't forget n = 0. That is the difference between (b) and (c).
Answer as per the official UPSC answer key.
Read the passage
Although most of the Genetically Modified (GM) crops cultivated now are genetically engineered for a single trait, in future, crops genetically engineered for more than one trait will be the norm. Thus, biotechnology’s role in agriculture and the regulation of the same cannot be understood solely in the context of the current generation of GM crops. Instead, there is a need to take a comprehensive look, taking into account various aspects, including socio-economic impacts, so that the potential of the technology can be harnessed while minimizing negative impacts. Given the importance of biotechnology in developing varieties that can help in climate change mitigation and adaptation, not using biotechnology as a part of the climate change action plan cannot be an option. Domestic regulation of biotechnology cannot be viewed in isolation of trade policy and obligations under various international treaties and conventions.
With reference to the above passage, the following assumptions have been made :
- 1. Biotechnology regulation is an evolving process.
- 2. Participation of people is needed in policy decisions regarding biotechnology regulation.
- 3. Biotechnology regulation should take into account socio-economic aspects in decision-making.
- 4. Wider involvement of political executive in biotechnology regulation improves its effectiveness in dealing with the country’s trade policies and international obligations.
Which of the above assumptions are valid?
Answer (b) & explanation
Assumptions 1 and 3 are valid (b). Step 1: the passage says regulation must look beyond "the current generation" of GM crops. So biotech regulation keeps evolving (1). Step 2: it says regulation must include "socio-economic impacts". So social and economic aspects count (3). Step 3: assumption 2, public participation, and assumption 4, a wider role for the political executive in trade policy, are not mentioned in the passage. So options (a), (c) and (d) fail.
Tip: check each statement against a line in the passage. If you cannot point to a line, the statement is not a valid assumption, however sensible it sounds. India's GM crop approvals are made by the Genetic Engineering Appraisal Committee (GEAC).
Answer as per the official UPSC answer key.
How many integers are there between 1 and 100 which have 4 as a digit but are not divisible by 4?
Answer (c) & explanation
12 such integers exist (c). Step 1: list the numbers from 1 to 100 with a 4 as a digit: 4, 14, 24, 34, 40 to 49 (ten numbers), 54, 64, 74, 84, 94. That is 19 numbers. Step 2: among them, those divisible by 4: 4, 24, 40, 44, 48, 64, 84. That is 7. Step 3: 19 − 7 = 12. Option (b), 11, and option (d), 13, miscount by one. Option (a) misses the 40s.
Tip: count the 40s block separately; it is easy to miss that 44 has two 4s but counts once. A number is divisible by 4 if its last two digits are divisible by 4.
Answer as per the official UPSC answer key.
The average score of a batsman after his 50th innings was 46·4. After 60th innings, his average score increases by 2·6. What was his average score in the last ten innings?
Answer (c) & explanation
His average in the last ten innings was 62 (c). Step 1: total after 50 innings = 50 × 46·4 = 2320. Step 2: the new average after 60 innings = 46·4 + 2·6 = 49. Total = 60 × 49 = 2940. Step 3: runs in the last 10 innings = 2940 − 2320 = 620. Average = 620 ÷ 10 = 62. Option (d), 49, is the new overall average. Options (a) and (b) fail.
Tip: always convert averages to totals before subtracting. Shortcut: the last 10 innings must lift 60 innings by 2·6 each and also match the old average: 46·4 + (60 × 2·6) ÷ 10 = 46·4 + 15·6 = 62.
Answer as per the official UPSC answer key.