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.
There is a milk sample with 50% water in it. If 1/3rd of this milk is added to equal amount of pure milk, then water in the new mixture will fall down to
Answer (a) & explanation
Water in the new mixture falls to 25% (a). Step 1: take 1 litre of the sample. It has 0.5 litre water and 0.5 litre milk. Step 2: add an equal amount, 1 litre, of pure milk. Now there are 2 litres, with still only 0.5 litre of water. Step 3: water = 0.5 ÷ 2 = 25%. The "1/3rd" only says how much of the sample is used. Since an equal amount of pure milk is added, the share is always halved. Options (b), (c) and (d) do not fit.
Tip: mixing a sample with an equal amount of a pure liquid halves the share of the other part. 50% water becomes 25%, whatever the quantity.
the 1/3rd is a distraction. Equal amounts halve the water share.
Answer as per the official UPSC answer key.
A, B, C, D, E, F and G are Lecturers from different cities—Hyderabad, Delhi, Shillong, Kanpur, Chennai, Mumbai and Srinagar (not necessarily in the same order) who participated in a conference. Each one of them is specialized in a different subject, viz., Economics, Commerce, History, Sociology, Geography, Mathematics and Statistics (not necessarily in the same order). Further
- 1. Lecturer from Kanpur is specialized in Geography
- 2. Lecturer D is from Shillong
- 3. Lecturer C from Delhi is specialized in Sociology
- 4. Lecturer B is specialized in neither History nor Mathematics
- 5. Lecturer A who is specialized in Economics does not belong to Hyderabad
- 6. Lecturer F who is specialized in Commerce belongs to Srinagar
- 7. Lecturer G who is specialized in Statistics belongs to Chennai
Who is specialized in Geography?
Answer (a) & explanation
B is specialised in Geography (a). Step 1: clues 3, 5, 6 and 7 fix four subjects: C has Sociology, A Economics, F Commerce and G Statistics. Step 2: the subjects left are History, Geography and Mathematics, for B, D and E. Step 3: clue 4 says B takes neither History nor Mathematics. So B takes Geography, and by clue 1 B is from Kanpur. Option (b) D and option (c) E share History and Mathematics. Option (d) fails because B is fixed.
Tip: in grid puzzles, first fill everything the clues state directly. Then use the "neither… nor" clue on the few gaps left. It usually settles one person at once.
Answer as per the official UPSC answer key.
There are three pillars X, Y and Z of different heights. Three spiders A, B and C start to climb on these pillars simultaneously. In one chance, A climbs on X by 6 cm but slips down 1 cm. B climbs on Y by 7 cm but slips down 3 cm. C climbs on Z by 6·5 cm but slips down 2 cm. If each of them requires 40 chances to reach the top of the pillars, what is the height of the shortest pillar?
Answer (b) & explanation
The shortest pillar is 163 cm (b). Step 1: in the last chance, each spider reaches the top and does not slip. So height = 39 × (net gain per chance) + one full climb. Step 2: A on X gains 6 − 1 = 5 per chance: 39 × 5 + 6 = 201 cm. B on Y gains 7 − 3 = 4: 39 × 4 + 7 = 163 cm. C on Z gains 6.5 − 2 = 4.5: 39 × 4.5 + 6.5 = 182 cm. Step 3: the shortest is 163 cm. Option (c), 182, is Z. Option (a), 161, and option (d), 210, are errors from counting slips in the 40th chance.
Tip: in climb-and-slip puzzles, the final climb has no slip. Count it separately.
40 × 4 = 160 forgets the last climb, which has no slip.
Answer as per the official UPSC answer key.
Read the passage
Many farmers use synthetic pesticides to kill infesting insects. The consumption of pesticides in some of the developed countries is touching 3000 grams/hectare. Unfortunately, there are reports that these compounds possess inherent toxicities that endanger the health of the farm operators, consumers and the environment. Synthetic pesticides are generally persistent in environment. Entering in food chain they destroy the microbial diversity and cause ecological imbalance. Their indiscriminate use has resulted in development of resistance among insects to insecticides, upsetting of balance in nature and resurgence of treated populations. Natural pest control using the botanical pesticides is safer to the user and the environment because they break down into harmless compounds within hours or days in the presence of sunlight. Plants with pesticidal properties have been in nature for millions of years without any ill or adverse effects on the ecosystem. They are easily decomposed by many microbes common in most soils. They help in the maintenance of biological diversity of predators and the reduction of environmental contamination and human health hazards. Botanical pesticides formulated from plants are biodegradable and their use in crop protection is a practical sustainable alternative.
Which of the following statements is/are correct regarding biopesticides?
- 1. They are not hazardous to human health.
- 2. They are persistent in environment.
- 3. They are essential to maintain the biodiversity of any ecosystem.
Select the correct answer using the code given below.
Answer (a) & explanation
Only statement 1 is correct (a). Step 1: the passage says biopesticides reduce "human health hazards" and are "safer to the user". So statement 1 holds. Step 2: statement 2 says they are persistent in the environment. But the passage says they break down within hours or days. That is the opposite of persistent. Step 3: statement 3 calls them essential to biodiversity. The passage says they help biodiversity, not that it cannot exist without them. So options (b), (c) and (d) fail.
Tip: "persistent" means a chemical stays in the environment for a long time, like DDT. Biopesticides are valued because they are not persistent.
Answer as per the official UPSC answer key.
What is the total number of digits printed, if a book containing 150 pages is to be numbered from 1 to 150?
Answer (b) & explanation
The total number of digits is 342 (b). Step 1: pages 1 to 9 use 1 digit each: 9 digits. Step 2: pages 10 to 99 are 90 pages with 2 digits each: 180 digits. Step 3: pages 100 to 150 are 51 pages with 3 digits each: 153 digits. Total = 9 + 180 + 153 = 342. Option (a), 262, and option (c), 360, are calculation slips. Option (d), 450, assumes 3 digits on every page.
Tip: split page numbers into 1-digit, 2-digit and 3-digit groups. Count pages in each group carefully: from 100 to 150 there are 51 pages, not 50.
Answer as per the official UPSC answer key.
Read the passage
There is more than a modicum of truth in the assertion that “a working knowledge of ancient history is necessary to the intelligent interpretation of current events”. But the sage who uttered these words of wisdom might well have added something on the benefits of studying particularly the famous battles of history for the lessons they contain for those of us who lead or aspire to leadership. Such a study will reveal certain qualities and attributes which enabled the winners to win—and certain deficiencies which caused the losers to lose. And the student will see that the same pattern recurs consistently, again and again, throughout the centuries.
With reference to the above passage, the following assumptions have been made :
- 1. A study of the famous battles of history would help us understand the modern warfare.
- 2. Studying the history is essential for anyone who aspires to be a leader.
Which of these assumptions is/are valid?
Answer (d) & explanation
Neither assumption is valid (d). Step 1: the passage says studying famous battles teaches qualities of leadership, such as courage and judgement. It does not say they explain modern warfare. So assumption 1 fails. Step 2: the passage calls studying history beneficial for leaders. Assumption 2 says it is essential for anyone who wants to lead. "Essential" is much stronger than "beneficial". Step 3: so assumption 2 fails too, and options (a), (b) and (c) fail.
Tip: watch the gap between "helpful" and "essential", or "useful" and "necessary". CSAT setters often swap a mild word for a strong one to make a statement false.
Answer as per the official UPSC answer key.
Consider the following :
A, B, C, D, E, F, G and H are standing in a row facing North.
B is not neighbour of G.
F is to the immediate right of G and neighbour of E.
G is not at the extreme end.
A is sixth to the left of E.
H is sixth to the right of C.
Which one of the following is correct in respect of the above?
Answer (c) & explanation
G is to the immediate right of D (c). Step 1: A is sixth to the left of E, and H is sixth to the right of C. In a row of 8, these pairs must take places 1–7 or 2–8. So A and C take places 1 and 2, and E and H take 7 and 8. Step 2: G, F, E sit together in that order. E must be 7, so F = 6 and G = 5. Then H = 8, A = 1 and C = 2. Step 3: B is not next to G, so B = 3 and D = 4. The row is A C B D G F E H. G is right of D. Options (a), (b) and (d) do not match this row.
Tip: place the "sixth to the left" pairs first; they leave few options.
Answer as per the official UPSC answer key.
Read the passage
By 2020, when the global economy is expected to run short of 56 million young people, India, with its youth surplus of 47 million, could fill the gap. It is in this context that labour reforms are often cited as the way to unlock double-digit growth in India. In 2014, India’s labour force was estimated to be about 40 per cent of the population, but 93 per cent of this force was in unorganized sector. Over the last decade, the compound annual growth rate (CAGR) of employment has slowed to 0·5 per cent, with about 14 million jobs created during last year when the labour force increased by about 15 million.
Which of the following is the most rational inference from the above passage?
Answer (b) & explanation
The rational inference is that labour reforms are needed to use India's large workforce productively (b). Step 1: the passage says about 93% of India's workforce is unorganised, and calls labour reform "the way to unlock double-digit growth". That is option (b). Step 2: option (c) says India will reach double-digit growth very soon. But the passage notes slow job growth, so that is not certain. Step 3: option (d) calls the youth skilled, which the passage never says. Option (a), population control, is not discussed.
Tip: an inference should not promise more than the passage. "Very soon" and "skilled" are added claims, so reject them. India's four labour codes, in force since 21 November 2025, are such a reform.
Answer as per the official UPSC answer key.
There are 4 horizontal and 4 vertical lines, parallel and equidistant to one another on a board. What is the maximum number of rectangles and squares that can be formed?
Answer (c) & explanation
The maximum number of rectangles and squares is 36 (c). Step 1: any rectangle, including a square, needs 2 horizontal lines and 2 vertical lines as its sides. Step 2: ways to pick 2 lines out of 4: (1,2), (1,3), (1,4), (2,3), (2,4), (3,4). That is 6 ways. Step 3: total = horizontal choices × vertical choices = 6 × 6 = 36. Four lines each way make a 3 × 3 grid, with only 9 small squares, so options (a), (b) and (d) undercount or overcount.
Tip: with m horizontal and n vertical lines, rectangles = (m choose 2) × (n choose 2). Squares are included in this count.
Answer as per the official UPSC answer key.
(Same information as the question above.)
To which city does the Lecturer specialized in Economics belong?
Answer (b) & explanation
The Economics lecturer is from Mumbai (b). Step 1: list the cities already fixed: C is from Delhi, D Shillong, F Srinagar and G Chennai. B teaches Geography, so B is from Kanpur. Step 2: that leaves Hyderabad and Mumbai for A and E. Step 3: A teaches Economics and is not from Hyderabad (clue 5). So A is from Mumbai. Option (a), Hyderabad, is ruled out by clue 5. Option (c) is wrong because one of the two must fit. Option (d) fails because the answer is clear.
Tip: when two people share two places, one "not" clue settles both. Keep track of the cities still free as you go.
Answer as per the official UPSC answer key.
Read the passage
“Rights are certain advantageous conditions of social well-being indispensable to the true development of the citizen.”
In the light of this statement, which one of the following is the correct understanding of rights?
Answer (c) & explanation
Rights aim at both individual and social good (c). Step 1: the statement calls rights conditions "of social well-being" that are needed for "the true development of the citizen". So rights serve society and the individual at once. That is option (c). Step 2: option (a), individual good only, keeps half of the definition. Option (b), social good only, keeps the other half. Step 3: option (d), individual good without social well-being, contradicts the words "social well-being".
Tip: options with "only" often cut a two-part definition in half. When a statement names two aims, pick the option that keeps both. This view of rights is linked to the thinker Harold Laski.
Answer as per the official UPSC answer key.
Certain 3-digit numbers have the following characteristics :
- 1. All the three digits are different.
- 2. The number is divisible by 7.
- 3. The number on reversing the digits is also divisible by 7.
How many such 3-digit numbers are there?
Answer (b) & explanation
There are 4 such numbers (b). Step 1: write the number as 100a + 10b + c. Number − reverse = 99(a − c). Both are divisible by 7, so 7 must divide 99(a − c). Since 7 does not divide 99, it must divide a − c. Step 2: the digits are all different, so a ≠ c. So a − c = ±7, giving end digits (1, 8), (8, 1), (2, 9), (9, 2). Step 3: test middle digits for each: 168, 861, 259 and 952 all work (168 = 7 × 24, 259 = 7 × 37). That is 4 numbers. Options (a), (c) and (d) do not fit.
Tip: number − reverse is always a multiple of 99 for 3-digit numbers. This fact unlocks many reversal puzzles.
Answer as per the official UPSC answer key.
Suppose the average weight of 9 persons is 50 kg. The average weight of the first 5 persons is 45 kg, whereas the average weight of the last 5 persons is 55 kg. Then the weight of the 5th person will be
Answer (c) & explanation
The 5th person weighs 50 kg (c). Step 1: total of all 9 = 9 × 50 = 450 kg. Step 2: total of the first 5 = 5 × 45 = 225 kg. Total of the last 5 = 5 × 55 = 275 kg. Step 3: the first five and the last five together make 10 people. But there are only 9, so the 5th person is counted twice. 225 + 275 − 450 = 50 kg. Option (a), 45 kg, is the first group's average. Options (b) and (d) are guesses between the averages.
Tip: when two groups overlap, add their totals and subtract the whole. What is left is the overlap. This trick saves time in many average questions.
Answer as per the official UPSC answer key.
In a certain code, '256' means 'red colour chalk', '589' means 'green colour flower' and '254' means 'white colour chalk'. The digit in the code that indicates 'white' is
Answer (b) & explanation
The digit for 'white' is 4 (b). Step 1: compare '256' = 'red colour chalk' with '254' = 'white colour chalk'. Step 2: both share the words colour and chalk, and both share the digits 2 and 5. Step 3: the only change is red to white, and 6 to 4. So white = 4. Option (c), 5, is shared by all three codes, so it means 'colour'. Option (a), 2, is shared by the chalk codes, so it means 'chalk'. Option (d), 8, belongs to 'green' or 'flower'.
Tip: in word-code questions, compare two codes that differ in only one word. The digit that changes is the code for that word.
Answer as per the official UPSC answer key.
Read the passage
The very first lesson that should be taught to us when we are old enough to understand it, is that complete freedom from the obligation to work is unnatural, and ought to be illegal, as we can escape our share of the burden of work only by throwing it on someone else’s shoulders. Nature ordains that the human race shall perish of famine if it stops working. We cannot escape from this tyranny. The question we have to settle is how much leisure we can afford to allow ourselves.
The main idea of the passage is that
Answer (a) & explanation
The main idea is that work is essential for human beings (a). Step 1: the passage says freedom from work is "unnatural", and humanity "shall perish of famine if it stops working". So work is necessary for survival. Step 2: option (b), a balance of work and leisure, is raised only near the end, not as the main idea. Step 3: option (c) calls work a tyranny we must face. The word "tyranny" is a figure of speech in the passage, not its message. Option (d), understanding the nature of work, is too vague.
Tip: the main idea is the claim the author repeats and backs with reasons. A colourful word used once is rarely the point.
Answer as per the official UPSC answer key.
A freight train left Delhi for Mumbai at an average speed of 40 km/hr. Two hours later, an express train left Delhi for Mumbai, following the freight train on a parallel track at an average speed of 60 km/hr. How far from Delhi would the express train meet the freight train?
Answer (c) & explanation
The express meets the freight train 240 km from Delhi (c). Step 1: the freight train has a 2-hour start at 40 km/hr. Its lead = 2 × 40 = 80 km. Step 2: the express is faster by 60 − 40 = 20 km/hr. This is the relative speed. The gap closes in 80 ÷ 20 = 4 hours. Step 3: in 4 hours the express covers 4 × 60 = 240 km. Check: the freight train has run 6 hours × 40 = 240 km. Option (d), 120 km, is the express's distance in 2 hours. Options (a) and (b) do not fit.
Tip: when one vehicle chases another in the same direction, subtract the speeds. The chase time = lead ÷ difference in speed.
Answer as per the official UPSC answer key.
(Same information as the question above.)
Who of the following belongs to Hyderabad?
Answer (b) & explanation
E belongs to Hyderabad (b). Step 1: from the earlier steps, C is from Delhi, D Shillong, F Srinagar, G Chennai and B Kanpur. Step 2: A, the Economics lecturer, is from Mumbai, because A is not from Hyderabad. Step 3: the only city left is Hyderabad, and the only person left is E. Option (a) B is from Kanpur. Option (c) is wrong because E fits. Option (d) fails because the data settle it.
Tip: linked questions in a set usually build on each other. Once you have solved the grid for one question, the next answers follow quickly. Keep your table on the page and do not solve it again.
Answer as per the official UPSC answer key.
15 students failed in a class of 52. After removing the names of failed students, a merit order list has been prepared in which the position of Ramesh is 22nd from the top. What is his position from the bottom?
Answer (c) & explanation
Ramesh is 16th from the bottom (c). Step 1: 15 of the 52 students failed and were removed. So the merit list has 52 − 15 = 37 names. Step 2: position from bottom = total − position from top + 1. Step 3: = 37 − 22 + 1 = 16th. Option (d), 15th, forgets to add 1. Option (a), 18th, and option (b), 17th, come from using the wrong total or adding wrongly. Check: 21 people above him, 15 below, plus him = 37.
Tip: use the "+1" rule in every rank question: top rank + bottom rank = total + 1. It works because the person is counted in both ranks.
don't use 52; the failed students are not in the list.
Answer as per the official UPSC answer key.
Examine the following statements :
- 1. All colours are pleasant.
- 2. Some colours are pleasant.
- 3. No colour is pleasant.
- 4. Some colours are not pleasant.
Given that statement 4 is true, what can be definitely concluded?
Answer (d) & explanation
Statement 1 is definitely false (d). Step 1: statement 4 says "some colours are not pleasant". Step 2: this is the exact opposite of statement 1, "all colours are pleasant". If some colours are not pleasant, then not all are. So 1 is false. Step 3: statement 2, "some colours are pleasant", could be true or false. Statement 3, "no colour is pleasant", could also be true or false. So options (a), (b) and (c) are not certain.
Tip: learn the opposite pairs: "all are" against "some are not", and "none are" against "some are". If one of a pair is true, the other is false. Other pairs tell you nothing for sure.
Answer as per the official UPSC answer key.
In a group of six women, there are four tennis players, four postgraduates in Sociology, one postgraduate in Commerce and three bank employees. Vimala and Kamla are the bank employees while Amala and Komala are unemployed. Komala and Nirmala are among the tennis players. Amala, Kamla, Komala and Nirmala are postgraduates in Sociology of whom two are bank employees. If Shyamala is a postgraduate in Commerce, who among the following is both a tennis player and a bank employee?
Answer (c) & explanation
Nirmala is both a tennis player and a bank employee (c). Step 1: Amala, Kamla, Komala and Nirmala are the four Sociology postgraduates, and two of them are bank employees. Step 2: Amala and Komala are unemployed. So the two bank employees among them are Kamla and Nirmala. Step 3: Komala and Nirmala are tennis players. So Nirmala is both a tennis player and a bank employee. Option (a) Amala and option (b) Komala are unemployed. Option (d) Shyamala is the Commerce postgraduate, and nothing makes her both.
Tip: in group puzzles, use the "unemployed" or "not" clues to rule people out first. The right person is then the one left in both groups.
Answer as per the official UPSC answer key.