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 angle between the minute hand and hour hand when the clock shows 4:25 hours?
Answer (c) & explanation
The angle is 17.5° (c). Step 1: the minute hand moves 6° a minute. At 25 minutes it is 25 × 6 = 150° from 12. Step 2: the hour hand moves 30° each hour and 0.5° each minute. At 4:25 it is 4 × 30 + 25 × 0.5 = 120 + 12.5 = 132.5°. Step 3: the gap is 150 − 132.5 = 17.5°. Option (a), 12.5°, is just the hour hand's extra movement. Options (b) and (d) are wrong.
Tip: use the formula angle = |30H − 5.5M|. Here |120 − 137.5| = 17.5°. If the answer is above 180°, subtract it from 360°.
(b) 15° forgets that the hour hand also moves during the 25 minutes.
Answer as per the official UPSC answer key.
Read the passage
The flower was not invented to please us. It flaunted its petals and spread its perfume to attract an insect. The insect carries the pollen from flower to flower so that pollen is not carried away by wind and thus not wasted. What we call a flower’s beauty is merely a by-product and a human invention. The perfume is not there to please us, it pleases us because it is there and we have been conditioned to it.
Based on the above passage, the following assumptions have been made :
- 1. The author of the passage believes that flowers are creations of Nature’s luxury.
- 2. The author of the passage does not believe in the usefulness of flowers except as things of beauty.
Which of the assumptions given above is/are valid?
Answer (d) & explanation
Neither assumption is valid (d). Step 1: the author says the flower's petals and perfume have a purpose: to attract insects that carry pollen, so it is not wasted. Step 2: assumption 1 calls flowers a "luxury" of Nature. But the author sees them as useful, not as luxury. Step 3: assumption 2 says the author sees flowers as useful only for beauty. The author says beauty is "merely a by-product" and a human idea. Both statements reverse the author's view, so options (a), (b) and (c) fail.
Tip: when a passage argues "X is not for Y but for Z", reject options that say X is for Y. Pollination by insects is a classic example of mutual benefit in nature.
Answer as per the official UPSC answer key.
A can X contains 399 litres of petrol and a can Y contains 532 litres of diesel. They are to be bottled in bottles of equal size so that whole of petrol and diesel would be separately bottled. The bottle capacity in terms of litres is an integer. How many different bottle sizes are possible?
Answer (b) & explanation
Four bottle sizes are possible (b). Step 1: the bottle size must divide both 399 and 532 exactly, so it must be a divisor of their HCF. Step 2: 399 = 3 × 7 × 19 and 532 = 4 × 7 × 19. HCF = 7 × 19 = 133. Step 3: divisors of 133 are 1, 7, 19 and 133: four sizes. Options (a), (c) and (d) miscount.
Tip: "how many sizes" means count the divisors of the HCF; "the largest size" means the HCF itself. To count divisors quickly, write the number as primes: 7¹ × 19¹ gives (1 + 1)(1 + 1) = 4.
Answer as per the official UPSC answer key.
Read the passage
When an international team of scientists pumped a carbon dioxide and water mix into underground basalt rocks, basic chemistry took over. The acidic mixture dissolved rocks’ calcium and magnesium and formed limestone. Basically carbon dioxide is converted into stone, exclaimed the scientists.
Which one of the following statements best reflects the most logical, rational and practical suggestion implied by the passage?
Answer (b) & explanation
The best suggestion is that this can be a method of carbon sequestration (b). Step 1: scientists pumped CO₂ and water into basalt rocks. The acid dissolved calcium and magnesium and formed limestone. Step 2: the key line is "carbon dioxide is converted into stone". Turning CO₂ into rock locks it away for good, which is carbon sequestration (capture and storage). So (b). Step 3: option (a), making commercial limestone, and (c), sourcing minerals, are side effects, not the point. Option (d) misreads the chemistry as an aim.
Tip: ask why the experiment matters, not just what happened. This idea, called mineral carbonation, is being tested in Iceland. It helps reach net-zero by removing CO₂ from the air.
Answer as per the official UPSC answer key.
Consider the following :
- 1. 1000 litres = 1 m3
- 2. 1 metric ton = 1000 kg
- 3. 1 hectare = 10000 m2
Which of the above are correct?
Answer (d) & explanation
All three statements are correct (d). Step 1: a cube 1 m on each side holds 1000 litres. So 1 m³ = 1000 L (1 is right). Step 2: a metric ton, also called a tonne, is 1000 kg (2 is right). Step 3: a hectare is a square field 100 m × 100 m, so 1 hectare = 10,000 m² (3 is right). So options (a), (b) and (c), which leave one out, are wrong.
Tip: learn these everyday conversions: 1 litre = 1000 cm³; 1 hectare is about 2.47 acres; 1 km² = 100 hectares. Land records and farm questions use hectares often.
Answer as per the official UPSC answer key.
Read the passage
Now-a-days there is a growing trend to use interconnected home devices. As consumers increasingly network their homes, the connected home device manufacturers and service providers will seek to overcome “thin profit margins by gathering more of our personal data—with or without our agreement—turning the home into a corporate storefront”. Corporate marketers will have powerful incentives to observe consumer behaviour to understand the buying needs and preferences of the device owners.
Which one of the following statements best reflects the most logical, rational and practical message implied by the passage?
Answer (d) & explanation
The message is that connected home devices can bring security and privacy risks (d). Step 1: the passage says device makers will gather "more of our personal data—with or without our agreement". Step 2: it says homes may become a "corporate storefront", with marketers watching consumer behaviour. That is a clear warning about privacy. So (d). Step 3: options (a) and (b) praise data use for industry and growth; the passage does not. Option (c), comfort and quality of life, is also not the passage's point.
Tip: catch the tone. Phrases like "with or without our agreement" signal a warning. India's Digital Personal Data Protection Act, 2023, requires consent for most data use.
Answer as per the official UPSC answer key.
How many consecutive zeros are there at the end of the integer obtained in the product 12 × 24 × 36 × 48 × … × 2550?
Answer (d) & explanation
There are 200 zeros at the end (d). Step 1: each trailing zero comes from one 2 and one 5. There are far more 2s than 5s, so just count the 5s. Step 2: the term k^(2k) gives 2k × (number of 5s in k). Only multiples of 5 matter: k = 5, 10, 15, 20 give 10 + 20 + 30 + 40 = 100. Step 3: k = 25 = 5 × 5 has two 5s, so it gives 2 × 25 × 2 = 100. Total = 200 fives, so 200 zeros. Options (a), (b) and (c) miss the extra 5s.
Tip: in zero-counting, numbers like 25, 125 hide extra 5s. Forgetting them is the most common trap.
(c) 100 is what you get if you forget that 25 carries two 5s.
Answer as per the official UPSC answer key.
Read the passage
Conventional classrooms, by emphasizing fixed duration over learning effectiveness, resign themselves to variable outcomes. The tyranny of the classroom is that every learner is subjected to the same set of lectures in the same way for the same duration. In the end, a few learners shine, some survive, and the rest are left behind. After the fixed duration, the classroom model moves on, with not a thought spared for those left behind. This is how we end up with 10 percent employability in our graduates after a decade and half of formal education. Repeating the same ineffectual script in the realm of skill education will not produce different results.
Which of the following statements best reflects/reflect the most logical and rational inference/inferences that can be made from the passage?
- 1. In conventional classroom learning, the central goal is duration of learning rather than attainment of competency.
- 2. Conventional classrooms encourage one-size-fits-all approach and stamp out all differentiation.
Select the correct answer using the code given below.
Answer (c) & explanation
Both inferences follow (c). Step 1: the passage says conventional classrooms emphasise "fixed duration over learning effectiveness". So the goal is time spent, not skill gained (1). Step 2: it calls it "the tyranny of the classroom" that every learner gets "the same set of lectures in the same way for the same duration". That is a one-size-fits-all approach that ignores differences among learners (2). Step 3: both ideas come straight from the text, so options (a), (b) and (d) fail.
Tip: when a statement paraphrases a key line, accept it. The passage's remedy is competency-based learning, where each learner moves on only after mastering a skill.
Answer as per the official UPSC answer key.
A Question is given followed by two Statements I and II. Consider the Question and the Statements.
Age of each of P and Q is less than 100 years but more than 10 years. If you interchange the digits of the age of P, the number represents the age of Q.
Question : What is the difference of their ages?
Statement-I : The age of P is greater than the age of Q.
Statement-II : The sum of their ages is 11/6 times their difference.
Which one of the following is correct in respect of the above Question and the Statements?
Answer (a) & explanation
Statement II alone is enough; Statement I alone is not (a). Step 1: let P's age be 10a + b and Q's be 10b + a. Sum = 11(a + b); difference = 9(a − b). Step 2: statement II: 11(a + b) = (11/6) × 9(a − b). So 2(a + b) = 3(a − b), giving a = 5b. Only b = 1, a = 5 works: ages 51 and 15, difference 36. Enough. Step 3: statement I only says P is older; many pairs fit (like 21 and 12, or 93 and 39). Not enough. So (a).
Tip: for reversed-digit numbers, remember: sum = 11 × (digit sum); difference = 9 × (digit gap). These two facts solve most such puzzles.
Answer as per the official UPSC answer key.
Consider the following statements in respect of the sum S = x + y + z, where x, y and z are distinct prime numbers each less than 10:
- 1. The unit digit of S can be 0.
- 2. The unit digit of S can be 9.
- 3. The unit digit of S can be 5.
Which of the statements given above are correct?
Answer (c) & explanation
Statements 1 and 3 are correct (c). Step 1: the primes below 10 are 2, 3, 5 and 7. We must pick three different ones, so there are only four possible sets. Step 2: list the sums: 2 + 3 + 5 = 10, 2 + 3 + 7 = 12, 2 + 5 + 7 = 14, 3 + 5 + 7 = 15. Step 3: unit digit 0 occurs (10), so 1 is true. Unit digit 5 occurs (15), so 3 is true. Unit digit 9 never occurs, so 2 is false. Options (a), (b) and (d) fail.
Tip: when the cases are few, simply list them all. Remember 1 is not a prime and 2 is the only even prime.
Answer as per the official UPSC answer key.
Read the passage
Geographers analyzed 175 satellite images of ocean colour, which is an indicator of phytoplankton productivity at the ocean’s surface, and found that giant icebergs are responsible for storing up to 20 percent of carbon in the Southern Ocean. The researchers discovered that melting water from giant icebergs which contains iron and other nutrients, supports hitherto unexpectedly high levels of phytoplankton growth.
Based on the above passage, the following assumptions have been made :
- 1. Giant icebergs have a bearing on primary productivity and food chains of the Southern Ocean.
- 2. Melting of giant icebergs can produce climate change effects and impact world fisheries.
Which of the assumptions given above is/are valid?
Answer (c) & explanation
Both assumptions are valid (c). Step 1: meltwater from giant icebergs carries iron and nutrients that boost phytoplankton. Phytoplankton are the base of the ocean food chain, so icebergs affect primary productivity and food chains (1). Step 2: icebergs help store up to 20 percent of the Southern Ocean's carbon. So changes in iceberg melting can affect the climate, and more or less plankton affects fish stocks (2). Step 3: both follow from the passage, so options (a), (b) and (d) fail.
Tip: remember the chain: nutrients → phytoplankton → fish. Phytoplankton also absorb CO₂ through photosynthesis, which is why oceans are a major carbon sink. Iron is often the missing nutrient in the Southern Ocean.
Answer as per the official UPSC answer key.
Read the passage
“The history of science is the real history of mankind.” In this striking epigram, a nineteenth-century writer links science with its background. Like most epigrams, its power lies in emphasizing by contrast an aspect of truth which may be easily overlooked. In this case, it is easy to overlook the relations between science and mankind, and to treat the former as some abstract third party, which can sometimes be praised for its beneficial influences, but frequently and conveniently blamed for the horrors of war. Science and mankind cannot be divorced from time to time at men’s convenience. Yet we have seen that, in spite of countless opportunities of improvement, the opening years of the present period of civilization have been dominated by international conflict. Is this the inevitable result of the progress of science or does the fault lie elsewhere?
Which of the following is/are emphatically conveyed by the author of the passage?
- 1. Without science, mankind could not have continued to exist till today.
- 2. It is the science that will ultimately determine the destiny of mankind.
Select the correct answer using the code given below.
Answer (d) & explanation
Neither statement is conveyed (d). Step 1: the author's main point is that science and mankind "cannot be divorced"; science is part of human history, not a separate "third party". Step 2: statement 1 says mankind could not have survived without science. The passage never says this. Statement 2 says science will decide mankind's destiny. The passage does not say this either. Step 3: in fact, the last question, "does the fault lie elsewhere?", hints that people, not science, may be to blame for wars. So options (a), (b) and (c) fail.
Tip: "emphatically conveyed" means the author clearly says it. Big claims like survival or destiny must be in the text, not just possible.
Answer as per the official UPSC answer key.
Read the passage
Green growth involves rethinking growth strategies with regard to the impacts on environmental sustainability and the environmental resources available to poor and vulnerable groups. In rethinking growth, we need to focus on the current reality of a resource-constrained world. Resource intensive and, in particular energy intensive processes will need to make way for more efficient and resource frugal development strategies if we are to avoid an economic dead end or a world in which only a small elite is able to enjoy affluence in the midst of a sea of poverty.
Which one of the following statements best reflects the crux of the above passage?
Answer (c) & explanation
The crux is that high environmental standards are now needed for steady, inclusive growth (c). Step 1: the passage says we live in a resource-constrained world. Energy-heavy processes must give way to efficient, frugal strategies. Step 2: otherwise we face "an economic dead end" (no steady growth) or a world where only "a small elite" is rich (no inclusive growth). So green growth is a must for good growth: (c). Step 3: options (a), (b) and (d) treat the environment and growth as enemies, or call degradation unavoidable. The passage argues the opposite.
Tip: "green growth" means growth and the environment going together. Reject options that set them against each other.
Answer as per the official UPSC answer key.
On January 1st, 2023, a person saved ₹ 1. On January 2nd, 2023, he saved ₹ 2 more than that on the previous day. On January 3rd, 2023, he saved ₹ 2 more than that on the previous day and so on. At the end of which date was his total savings a perfect square as well a perfect cube?
Answer (b) & explanation
His total was a perfect square and cube on 8th January (b). Step 1: daily savings are 1, 3, 5, 7, … (odd numbers). The sum of the first n odd numbers = n². So after n days he has n² rupees. Step 2: n² is also a perfect cube only when n itself is a cube: n = 1, 8, 27, … Step 3: n = 8 gives 8² = 64 = 4³, both a square and a cube. So the 8th day, 8th January. Option (a) gives 49 (not a cube); (c) gives 81 (not a cube). Option (d) is wrong.
Tip: remember 1 + 3 + 5 + … (n terms) = n². A number that is both a square and a cube is a sixth power: 1, 64, 729.
Answer as per the official UPSC answer key.
Read the passage
Conventional classrooms, by emphasizing fixed duration over learning effectiveness, resign themselves to variable outcomes. The tyranny of the classroom is that every learner is subjected to the same set of lectures in the same way for the same duration. In the end, a few learners shine, some survive, and the rest are left behind. After the fixed duration, the classroom model moves on, with not a thought spared for those left behind. This is how we end up with 10 percent employability in our graduates after a decade and half of formal education. Repeating the same ineffectual script in the realm of skill education will not produce different results.
Based on the above passage, the following assumptions have been made :
- 1. As a large number of workers in our country are employed in unorganized sector, India does not need to change its present conventional classroom system of education.
- 2. Even with its present conventional classroom system of education, India produces sufficient number of skilled workers to fully realize the benefits of demographic dividend.
Which of the assumptions given above is/are valid?
Answer (d) & explanation
Neither assumption is valid (d). Step 1: the passage attacks the classroom system: some learners are left behind and only 10 percent of graduates are employable. It warns that copying this model in skill education will fail. Step 2: assumption 1 says India need not change its system. Assumption 2 says the present system produces enough skilled workers. Both defend the current system, the exact opposite of the passage. Step 3: the unorganised sector is not even mentioned. So options (a), (b) and (c) fail.
Tip: an assumption must agree with the author's line of argument. If a statement contradicts the author's conclusion, reject it at once.
Answer as per the official UPSC answer key.
A Main Statement is followed by four Statements labelled P, Q, R and S. Choose the ordered pair of the Statements where the first Statement implies the second, and the two Statements are logically consistent with the Main Statement.
Main Statement : Pradeep becomes either a Director or a Producer.
Statement P : Pradeep is a Director.
Statement Q : Pradeep is a Producer.
Statement R : Pradeep is not a Director.
Statement S : Pradeep is not a Producer.
Select the correct answer.
Answer (c) & explanation
Both SP and RQ are valid pairs (c). Step 1: the main statement says Pradeep becomes either a Director or a Producer. So if one is false, the other must be true. Step 2: S, "not a Producer", implies P, "a Director". So SP works. Step 3: R, "not a Director", implies Q, "a Producer". So RQ works too. Both pairs are consistent with the main statement. Options (a), (b) and (d) leave one out.
Tip: for "either A or B", the valid pairs are always "not A → B" and "not B → A". The pairs "A → not B" are not safe, because both might be true.
the pair must start with a negative (not X) and end with the other choice (Y), never the other way round.
Answer as per the official UPSC answer key.
Read the passage
By the time children reach class 8, the bulk of them tend to be in the age range of 13 years to 15 years. But in our country, about a quarter of all children in class 8 struggle with reading simple texts and more than half are still unable to do basic arithmetic operations like division. Every year about 25 million young boys and girls from elementary school move into the life that lies for them beyond compulsory schooling. They cannot enter the workforce at least in the organized sector till they are 18. For many families, these children are the first from their families ever to get this far in school. Parents and children expect that such ‘graduates’ from school will go on to high school and college. Hardly anyone wants to go back to agriculture. On the other hand, abilities in terms of academic competencies are far lower than they should be even based on curricular expectations of class 8.
Based on the above passage, the following assumptions have been made :
- 1. For effective school education, parents have greater role than the governments.
- 2. School curriculum that conforms to today’s requirements and is uniform for the entire country may address the issues brought out.
Which of the assumptions given above is/are valid?
Answer (d) & explanation
Neither assumption is valid (d). Step 1: assumption 1 says parents have a bigger role than governments. The passage mentions parents' expectations, but never compares their role with the government's. Step 2: assumption 2 suggests a uniform national curriculum. The passage says children fall short even of the existing class 8 curriculum. So the problem is learning, not the curriculum design; the passage proposes no uniform syllabus. Step 3: so options (a), (b) and (c) fail.
Tip: an assumption must be needed by the passage. Solutions the author never suggests are not assumptions. Surveys like ASER report similar gaps in basic reading and arithmetic.
Answer as per the official UPSC answer key.
Read the passage
Evolution has endowed caterpillars that feed on corn with a unique ability, they can induce the plant to turn off its defence against insect predators. This helps caterpillars to eat more and grow faster. The agent that causes this effect is the caterpillar’s faeces or frass. The find could throw new light on compounds associated with plant response to pathogens like fungi or bacteria.
Which one of the following statements best reflects the most logical, rational and practical message conveyed by the passage?
Answer (c) & explanation
The practical message is that this can help develop organic, eco-friendly pesticides (c). Step 1: caterpillars make the corn plant switch off its defences through a natural compound in their droppings (frass). Step 2: once we understand how this switch works, we can find ways to keep plant defences on, a natural, chemical-free way to protect crops. That points to sustainable pest control, as UPSC's key takes it. Step 3: option (a), using caterpillars on weeds, is not suggested. Option (b), medical antimicrobials, goes beyond plants. Option (d), genetically modified caterpillars, is far-fetched.
Tip: in "practical message" questions, choose the option closest to the field of the passage, here crops and pests, not medicine. Biological pest control is part of integrated pest management.
Answer as per the official UPSC answer key.
Read the passage
“The history of science is the real history of mankind.” In this striking epigram, a nineteenth-century writer links science with its background. Like most epigrams, its power lies in emphasizing by contrast an aspect of truth which may be easily overlooked. In this case, it is easy to overlook the relations between science and mankind, and to treat the former as some abstract third party, which can sometimes be praised for its beneficial influences, but frequently and conveniently blamed for the horrors of war. Science and mankind cannot be divorced from time to time at men’s convenience. Yet we have seen that, in spite of countless opportunities of improvement, the opening years of the present period of civilization have been dominated by international conflict. Is this the inevitable result of the progress of science or does the fault lie elsewhere?
Based on the above passage, the following assumptions have been made :
- 1. The horrors of modern life are the inevitable result of the progress of science.
- 2. The aspect of truth likely to be overlooked is that science is what man has made it.
Which of the assumptions given above is/are correct?
Answer (b) & explanation
Only assumption 2 is correct (b). Step 1: the passage says people wrongly treat science as an "abstract third party" that can be praised or blamed. The overlooked truth is that science belongs to mankind; it is what man makes of it (2). Step 2: assumption 1 says the horrors of modern life are the inevitable result of science. The author only asks this as a question ("Is this the inevitable result...?") and hints the fault may lie elsewhere. Step 3: so 1 is not assumed. Options (a), (c) and (d) fail.
Tip: a question asked by the author is not the author's belief. Read the closing question as a doubt, not a claim.
Answer as per the official UPSC answer key.
A Question is given followed by two Statements I and II. Consider the Question and the Statements.
Question : What are the unique values of x and y, where x, y are distinct natural numbers?
Statement-I : x/y is odd.
Statement-II : xy = 12
Which one of the following is correct in respect of the above Question and the Statements?
Answer (c) & explanation
Both statements together are needed (c). Step 1: statement I: x/y is odd. Endless pairs work, like (3, 1), (5, 1), (6, 2). Not enough. Step 2: statement II: xy = 12 with distinct numbers: (1, 12), (2, 6), (3, 4) and their reverses. Not enough. Step 3: together, check x/y for each pair: 12/1 = 12 (even), 6/2 = 3 (odd), 4/3 is not whole. Only x = 6, y = 2 works. Unique. Options (a), (b) and (d) fail.
Tip: list all cases from the more limited statement, then filter them with the other. If exactly one survives, both are needed together.
Answer as per the official UPSC answer key.