UPSC Prelims PYQs with explanations
Real questions from official papers, mapped to syllabus topics. Attempt each one; the answer and the reason appear instantly.
The difference between any two natural numbers is 10. What can be said about the natural numbers which are divisible by 5 and lie between these two numbers?
Answer (c) & explanation
There can be more than one such number (c). Step 1: take two numbers 10 apart, such as 5 and 15. Strictly between them, only 10 is divisible by 5. That is one number. Step 2: now take 1 and 11. Between them, 5 and 10 are divisible by 5. That is two numbers. Step 3: the count can be one or two depending on the pair. So "only one" (a) and "only two" (b) are not always true, and (d) is false. The safe statement is (c): there can be more than one.
Tip: test both an "edge" case (ends are multiples of 5) and a general case. When answers vary, pick the option that allows for it.
Answer as per the official UPSC answer key.
Consider the following statements :
- Statement I : Article 6 of the Paris Agreement on climate change is frequently discussed in global discussions on sustainable development and climate change.
- Statement II : Article 6 of the Paris Agreement on climate change sets out the principles of carbon markets.
- Statement III : Article 6 of the Paris Agreement on climate change intends to promote inter-country non-market strategies to reach their climate targets.
Which one of the following is correct in respect of the above statements?
Answer (a) & explanation
Both II and III are correct and both explain Statement I (a). Article 6 of the Paris Agreement lets countries work together to meet their targets. Statement II is right: Articles 6.2 and 6.4 set up carbon markets, for trading credits between countries and through a UN-run mechanism. Statement III is right: Article 6.8 covers non-market approaches, such as joint finance, technology and capacity building. Both halves are why it is discussed so much, so options (b), (c) and (d) fail.
Notice the progress: rules for Article 6 carbon markets were finally agreed at COP29 in Baku (2024). India's own Carbon Credit Trading Scheme (2023) builds a domestic market, and India has signed Article 6.2 deals, such as with Japan.
Answer as per the official UPSC answer key.
Consider the following statements in respect of RTGS and NEFT :
- I. In RTGS, the settlement time is instantaneous while in case of NEFT, it takes some time to settle payments.
- II. In RTGS, the customer is charged for inward transactions while that is not the case for NEFT.
- III. Operating hours for RTGS are restricted on certain days while this is not true for NEFT.
Which of the statements given above is/are correct?
Answer (a) & explanation
Only statement I is correct (a). Statement I is right: RTGS settles each payment one by one, in real time, while NEFT settles in half-hourly batches, so it takes a little time. Statement II is wrong: no bank charges for inward RTGS or NEFT credits; the RBI also waived its charges on outward online transfers for savings accounts. Statement III is wrong: both systems run 24×7, 365 days: NEFT since December 2019 and RTGS since December 2020. So options (b), (c) and (d) fail.
Notice the limits: RTGS has a minimum of ₹2 lakh, with no upper limit; NEFT has no minimum. IMPS and UPI, run by NPCI, give instant transfers too. The RBI runs RTGS and NEFT itself.
statement III was true before 2020. UPSC often tests the latest position, not what older books say.
Answer as per the official UPSC answer key.
Consider the following statements :
- I. In the finals of the 45th Chess Olympiad held in 2024, Gukesh Dommaraju became the world’s youngest winner after defeating the Russian player Ian Nepomniachtchi.
- II. Abhimanyu Mishra, an American chess player, holds the record of becoming world’s youngest ever Grandmaster.
Which of the statements given above is/are correct?
Answer (b) & explanation
Only statement II is correct (b). Statement II is right: Abhimanyu Mishra of the USA became the youngest-ever grandmaster in 2021, at 12 years and 4 months, beating Sergey Karjakin's record. Statement I is wrong: India won gold at the 45th Chess Olympiad (Budapest, 2024), but the Olympiad is a team event with no final. Gukesh became the youngest World Champion by beating Ding Liren of China in December 2024, not Nepomniachtchi. So options (a), (c) and (d) fail.
Notice India's golden year: both the open and women's teams won Olympiad gold in 2024. Divya Deshmukh won the Women's World Cup in 2025. Viswanathan Anand was India's first grandmaster (1988).
Answer as per the official UPSC answer key.
Let both p and k be prime numbers such that (p2 + k) is also a prime number less than 30. What is the number of possible values of k?
Answer (b) & explanation
Five values of k are possible (b). Step 1: if p = 2, then p² = 4, and 4 + k must be a prime below 30. k = 3, 7, 13, 19 work (sums 7, 11, 17, 23). k = 2 gives 6, not prime. Step 2: if p is odd, p² is odd, so k must be 2 (the even prime) to keep the sum odd. p = 3 gives 9 + 2 = 11, prime. p = 5 gives 27, not prime. So k = 2 also works. Step 3: possible k: 2, 3, 7, 13, 19 = 5 values. Options (a), (c) and (d) miscount.
Tip: in prime questions, split into "2" and "odd" cases. Odd + odd is even, so the even prime 2 often decides things.
Answer as per the official UPSC answer key.
X can complete one-third of a certain work in 6 days, Y can complete one-third of the same work in 8 days and Z can complete three-fourth of the same work in 12 days. All of them work together for n days and then X and Z quit and Y alone finishes the remaining work in 8 2/3 days. What is n equal to?
Answer (b) & explanation
n is 4 days (b). Step 1: find each person's full time. X does 1/3 in 6 days, so the whole work in 18 days. Y: 1/3 in 8 days, so 24 days. Z: 3/4 in 12 days, so 16 days. Step 2: together per day: 1/18 + 1/24 + 1/16 = 8/144 + 6/144 + 9/144 = 23/144. Step 3: Y alone works 8⅔ = 26/3 days: (26/3) × (1/24) = 26/72 = 52/144. The rest, 92/144, was done together: 23n/144 = 92/144, so n = 4. Options (a), (c) and (d) fail.
Tip: turn part-work into full-work days first. Use the LCM (here 144) as the total work to avoid fractions.
Answer as per the official UPSC answer key.
Consider the following subjects with regard to Non-Cooperation Programme :
- I. Boycott of law-courts and foreign cloth
- II. Observance of strict non-violence
- III. Retention of titles and honours without using them in public
- IV. Establishment of Panchayats for settling disputes
How many of the above were parts of Non-Cooperation Programme?
Answer (c) & explanation
Three of the four were part of the programme (c). The Nagpur Congress (December 1920) approved the Non-Cooperation programme. Item I is right: it asked people to boycott law-courts, schools, councils and foreign cloth. Item II is right: it demanded strict non-violence. Item IV is right: it asked people to set up panchayats to settle disputes outside British courts. Item III is wrong: people were asked to surrender titles and honours, not keep them.
Notice the positive side: national schools such as Jamia Millia Islamia and Kashi Vidyapith, khadi and the Tilak Swaraj Fund. Gandhi called off the movement after the Chauri Chaura violence in February 1922. He also returned his Kaisar-i-Hind medal.
"Retention" is the word to catch. The programme said surrender.
Answer as per the official UPSC answer key.
Consider the following substances :
- I. Ethanol
- II. Nitroglycerine
- III. Urea
Coal gasification technology can be used in the production of how many of them?
Answer (b) & explanation
Coal gasification can produce two of them (b). Gasification turns coal into syngas, a mix of carbon monoxide and hydrogen. Item III is right: syngas can be made into ammonia and then urea, as at the revived Talcher fertiliser plant. Item I is right: syngas can be made into methanol and ethanol, which is why India's coal gasification mission names these products. Item II is wrong: nitroglycerine is made by nitrating glycerol, which comes from fats, not from syngas.
Notice the National Coal Gasification Mission, aiming to gasify 100 million tonnes of coal by 2030, to cut imports of gas, ammonia and methanol. Gasification is cleaner than burning coal directly, but still emits CO₂.
Answer as per the official UPSC answer key.
Consider the following pairs :
| Country | Resource-rich in
| I. Botswana | Diamond
| II. Chile | Lithium
| III. Indonesia | Nickel
In how many of the above rows is the given information correctly matched?
Answer (c) & explanation
All three rows are correctly matched (c). Row I is right: Botswana is among the top diamond producers, from mines such as Jwaneng, one of the richest. Row II is right: Chile has the world's largest lithium reserves, in the Atacama salt flats. Row III is right: Indonesia is the largest nickel producer, and has banned raw ore exports to build its own processing. So options (a), (b) and (d) fail.
Notice the "Lithium Triangle": Chile, Argentina and Bolivia together hold most of the world's lithium. India's KABIL has bought lithium blocks in Argentina. Nickel and lithium are both critical minerals for EV batteries, and Indonesia's ore ban is a model of resource nationalism.
Answer as per the official UPSC answer key.
Three prime numbers p, q and r, each less than 20, are such that p – q = q – r. How many distinct possible values can we get for (p + q + r)?
Answer (d) & explanation
More than 6 sums are possible (d). Step 1: p − q = q − r means p + r = 2q, so the sum p + q + r = 3q. Each different q gives a different sum. Step 2: the question does not say the primes must be different. So p = q = r is allowed (for example, 7 − 7 = 7 − 7). Then every prime below 20 can be q: 2, 3, 5, 7, 11, 13, 17, 19. Step 3: that gives 8 sums, which is more than 6. Options (a), (b) and (c) assume the primes must be distinct.
Tip: read the conditions closely. If a question does not say "distinct", equal values are allowed, and that often changes the answer.
read what is not said. Without "distinct", equal primes are allowed. With distinct primes you would get only 4 (q = 5, 7, 11, 13).
Answer as per the official UPSC answer key.
If P = +, Q = –, R = ×, S = ÷, then insert the proper notations between the successive numbers in the equation 60 _ 15 _ 3 _ 20 _ 4 = 20 :
Answer (b) & explanation
The correct order is QRPS (b). Step 1: decode: P = +, Q = −, R = ×, S = ÷. Step 2: test (b) QRPS: 60 − 15 × 3 + 20 ÷ 4. Do × and ÷ first: 15 × 3 = 45 and 20 ÷ 4 = 5. Then 60 − 45 + 5 = 20 ✓. Step 3: test (a) SPRQ: 60 ÷ 15 + 3 × 20 − 4 = 4 + 60 − 4 = 60 ✗. Option (c) QRSP gives 60 − 15 × 3 ÷ 20 + 4 = 61.75, and (d) SPQR gives 4 + 3 − 80 = −73.
Tip: test the options rather than building the answer yourself. Always apply BODMAS: × and ÷ before + and −.
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 and mark the correct option.
Question: How is Q related to P?
Statement I: P has two sisters, R and S.
Statement II: R's father is the brother of Q.
Which one of the following is correct in respect of the above Question and the Statements?
Answer (d) & explanation
Even both statements together are not enough (d). Step 1: statement I says P has two sisters, R and S. So R is P's sibling. Step 2: statement II says R's father is Q's brother. R's father is also P's father. So Q is a sibling of P's father. Step 3: Q could be P's uncle (if male) or aunt (if female). Q's gender is not given, so the exact relation cannot be fixed. Options (a), (b) and (c) fail.
Tip: in relation questions, check that the gender of the person asked about is known. "Brother of Q" tells us about the brother, not about Q.
Answer as per the official UPSC answer key.
Consider the following statements about turmeric during the year 2022-23 :
- I. India is the largest producer and exporter of turmeric in the world.
- II. More than 30 varieties of turmeric are grown in India.
- III. Maharashtra, Telangana, Karnataka and Tamil Nadu are major turmeric producing States in India.
Which of the statements given above are correct?
Answer (d) & explanation
All three statements are correct (d). Statement I is right: in 2022-23, India grew over 75% of the world's turmeric and had more than 62% of world trade. Statement II is right: more than 30 varieties are grown in over 20 States. Statement III is right: the major producers are Maharashtra, Telangana, Karnataka and Tamil Nadu. These lines come from the government's note on setting up the National Turmeric Board (2023).
Notice the board, based at Nizamabad in Telangana, which promotes turmeric research, exports and value addition. Turmeric's active compound is curcumin. Famous GI-tagged varieties include Erode turmeric, Lakadong turmeric of Meghalaya and Kandhamal Haladi of Odisha.
Answer as per the official UPSC answer key.
Consider the following subjects under the Constitution of India :
- I. List I-Union List, in the Seventh Schedule
- II. Extent of the executive power of a State
- III. Conditions of the Governor's office
For a constitutional amendment with respect to which of the above, ratification by the Legislatures of not less than one-half of the States is required before presenting the bill to the President of India for assent?
Answer (a) & explanation
Items I and II need ratification by half the States (a). The proviso to Article 368(2) lists the federal subjects that need ratification by half the State legislatures. Item I is right: it includes any of the Lists in the Seventh Schedule. Item II is right: it includes Article 162, on the extent of a State's executive power. Item III is wrong: the Governor's conditions of office (Article 158) are not on that list, so Parliament alone can amend them. So options (b), (c) and (d) fail.
Notice other items needing ratification: election of the President (Articles 54, 55), the Supreme Court and High Courts, representation of States in Parliament, and Article 368 itself. The GST (101st Amendment) needed ratification because it changed the Lists.
the Governor feels "federal", but Article 158 is not in the ratification list.
Answer as per the official UPSC answer key.
Which organization has enacted the Nature Restoration Law (NRL) to tackle climate change and biodiversity loss?
Answer (a) & explanation
The European Union enacted the Nature Restoration Law (a). The European Union adopted its Nature Restoration Law in 2024. It requires member states to restore at least 20% of the EU's damaged land and sea areas by 2030, and all ecosystems in need by 2050. Options (b), (c) and (d) are wrong: only a body that makes laws can "enact" one. The World Bank, OECD and FAO give loans, advice or technical help, but cannot pass binding laws.
Notice the link to the Kunming-Montreal Global Biodiversity Framework (2022), whose "30 by 30" target asks for 30% of land and sea to be protected by 2030. The EU law faced strong protests from farmers before it passed narrowly.
Answer as per the official UPSC answer key.
The petrol price shot up by 10% as a result of the hike in crude oil prices. The price of petrol before the hike was ₹ 90 per litre. A person travels 2200 km every month and his car gives a mileage of 16 km per litre. By how many km should he reduce his travel if he wants to maintain his expenditure at the previous level?
Answer (b) & explanation
He must cut his travel by 200 km (b). Step 1: to keep spending the same, price × litres must stay fixed. The price rises by 10%, from ₹90 to ₹99, so the litres he buys must fall to 100/110 = 10/11 of before. Step 2: his travel falls in the same ratio: 2200 × 10/11 = 2000 km. Step 3: so he must reduce by 2200 − 2000 = 200 km. The mileage (16 km/l) is not needed. Option (c), 220 km, wrongly takes 10% of 2200.
Tip: a 10% price rise needs a cut of 10/110 = 1/11 (about 9.1%) in use, not 10%, to keep spending the same.
a 10% rise needs a 1/11 cut (about 9.1%), not a 10% cut of 220 km.
Answer as per the official UPSC answer key.
A mobile phone has been stolen. There are 3 suspects P, Q and R. They were questioned knowing that only one of them is guilty. Their responses are as follows :
P : I did not steal. Q stole it.
Q : R did not steal. I did not steal.
R : I did not steal. I do not know who did it.
Who stole the mobile phone?
Answer (d) & explanation
The thief cannot be concluded (d). Step 1: we know only one is guilty, but we are not told who speaks the truth or how many lie. Step 2: test each case. If P stole it, P lies, and Q and R can both be telling the truth. If Q stole it, Q lies, and P and R can be truthful. If R stole it, R lies, and Q's "R did not steal" is false, while P's "Q stole it" is false too. Step 3: without a rule like "only one lies", several cases fit. So no one can be named. Options (a), (b) and (c) fail.
Tip: in truth-teller puzzles, look for a rule about who lies. If none is given, the answer is often "cannot be concluded".
don't assume the innocent always tell the truth unless the question says so.
UPSC repeats traps like this year after year. The PYQ Book gathers every trap in one place, so you see them coming. Try the free sample
Answer as per the official UPSC answer key.
With reference to investments, consider the following :
- I. Bonds
- II. Hedge Funds
- III. Stocks
- IV. Venture Capital
How many of the above are treated as Alternative Investment Funds?
Answer (b) & explanation
Only two are Alternative Investment Funds (b). Under SEBI's AIF Regulations, 2012, an Alternative Investment Fund is a privately pooled fund that collects money from rich or institutional investors and invests it under a set policy. Item IV is right: venture capital funds fall in Category I. Item II is right: hedge funds fall in Category III, as they use complex trading and borrowing. Items I and III are wrong: bonds and stocks are ordinary securities that anyone can buy on the market; they are not funds at all.
Notice the three categories: Category I (venture capital, SME and infrastructure funds), Category II (private equity, debt funds) and Category III (hedge funds). The minimum investment is usually ₹1 crore.
bonds and stocks are "investments", but the question asks about funds.
Answer as per the official UPSC answer key.
Which one of the following launched the ‘Nature Solutions Finance Hub for Asia and the Pacific’?
Answer (a) & explanation
The Asian Development Bank launched the hub (a). The Asian Development Bank (ADB) launched the Nature Solutions Finance Hub for Asia and the Pacific in 2024. It aims to draw private money, at least $2 billion, into projects that protect or restore nature, such as mangroves, forests and watersheds. Option (b) is wrong: the AIIB, based in Beijing, did not launch it. Option (c) is wrong: the New Development Bank is the BRICS bank in Shanghai. Option (d) is wrong: the IBRD is the main lending arm of the World Bank.
Notice that the ADB is based in Manila, set up in 1966, with Japan and the USA as top shareholders. India is a founder member and among its largest borrowers.
Answer as per the official UPSC answer key.
Consider the following countries :
- I. United Arab Emirates
- II. France
- III. Germany
- IV. Singapore
- V. Bangladesh
How many countries amongst the above are there other than India where international merchant payments are accepted under UPI?
Answer (b) & explanation
Three of the listed countries accept UPI merchant payments (b). NPCI International has taken UPI merchant payments to the UAE, France, starting with the Eiffel Tower, and Singapore, among others such as Bhutan, Nepal, Sri Lanka and Mauritius. Items III and V are wrong: Germany and Bangladesh were not on that list when the question was set. So options (a), (c) and (d) fail.
Notice the Singapore link: UPI was joined to Singapore's PayNow in 2023 for instant cross-border transfers. UPI handles most of India's digital payments, over 20 billion transactions a month. The RuPay card is UPI's partner in the push abroad. Expansion abroad continues, so check the latest list before an exam.
Answer as per the official UPSC answer key.