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 average weight of A, B, C is 40 kg, the average weight of B, D, E is 42 kg and the weight of F is equal to that of B. What is the average weight of A, B, C, D, E and F?
Answer (c) & explanation
The average weight is 41 kg (c). Step 1: A + B + C = 3 × 40 = 120. B + D + E = 3 × 42 = 126. Step 2: adding them gives A + 2B + C + D + E = 246. Since F = B, this is just A + B + C + D + E + F = 246. Step 3: average = 246 ÷ 6 = 41 kg. Option (d) is wrong: F = B fills the gap. Options (a) and (b) are miscalculations.
Tip: when a person is counted twice, look for a clue that replaces the double count (here F = B).
it looks as if B is needed, but F = B makes it cancel out.
One trap spotted is one mark saved. The PYQ Book lines up every trap UPSC has set, so you walk in prepared. Try the free sample
Answer as per the official UPSC answer key.
Which one of the following statements best reflects the idea behind the “Fractional Orbital Bombardment System” often talked about in media ?
Answer (c) & explanation
FOBS puts a missile in orbit and brings it down on a target (c). The Fractional Orbital Bombardment System is a Soviet idea from the 1960s. It sends a warhead into a partial low orbit and brings it down over the target from any direction, even over the South Pole. This avoids early-warning radars, which mostly look north, and leaves no fixed path. Option (a) describes planetary defence against asteroids. Option (b) describes a planetary landing. Option (d) describes a comet mission, such as Rosetta.
Notice that reports of China's 2021 hypersonic glide test via orbit brought FOBS back into the news. The Outer Space Treaty (1967) bans placing nuclear weapons in orbit. India tested an anti-satellite missile in Mission Shakti (2019).
Answer as per the official UPSC answer key.
Consider the following statements :
- 1. Vietnam has been one of the fastest growing economies in the world in the recent years.
- 2. Vietnam is led by a multi-party political system.
- 3. Vietnam's economic growth is linked to its integration with global supply chains and focus on exports.
- 4. For a long time Vietnam's low labour costs and stable exchange rates have attracted global manufacturers.
- 5. Vietnam has the most productive e-service sector in the Indo-Pacific region.
Which of the statements given above are correct ?
Answer (c) & explanation
Statements 1, 3 and 4 are correct (c). Statement 1 is right: Vietnam has grown at about 6–7% a year for most of the past decade, among the fastest anywhere. Statement 3 is right: that growth comes from joining global supply chains and exporting electronics, phones and garments. Statement 4 is right: low wages and a stable currency drew makers such as Samsung, and many firms moving out of China. Statement 2 is wrong: Vietnam is a one-party state run by the Communist Party. Statement 5 is wrong: nothing marks its e-services as the region's most productive.
Notice the "China plus one" strategy, under which companies add a second base outside China. Vietnam is India's main rival for these factories, which India chases through PLI schemes.
Answer as per the official UPSC answer key.
Consider the following :
- 1. Carbon monoxide
- 2. Nitrogen oxide
- 3. Ozone
- 4. Sulphur dioxide
Excess of which of the above in the environment is/are cause(s) of acid rain ?
Answer (b) & explanation
Nitrogen oxides and sulphur dioxide cause acid rain (b). Sulphur dioxide (SO₂), mostly from burning coal and oil, and nitrogen oxides (NOₓ), mostly from vehicles and power plants, react with water in the air to form sulphuric and nitric acids. These fall as acid rain, with a pH below about 5.6. Item 1 is wrong: carbon monoxide is a poisonous gas but does not make rain acidic. Item 3 is wrong: ozone at ground level is a harmful smog pollutant, but it is not an acid-forming gas. So options (a), (c) and (d) fall.
Notice the famous Indian case: the yellowing of the Taj Mahal was blamed partly on SO₂ from the Mathura refinery, which led to the Taj Trapezium Zone.
Answer as per the official UPSC answer key.
A, B and C are three places such that there are three different roads from A to B, four different roads from B to C and three different roads from A to C. In how many different ways can one travel from A to C using these roads?
Answer (c) & explanation
There are 15 ways (c). Step 1: going A to B and then B to C: 3 × 4 = 12 ways. For "and then", multiply. Step 2: going directly from A to C: 3 ways. Step 3: the two routes are alternatives, so add: 12 + 3 = 15. Option (a), 10, adds all the numbers. Option (b), 13, misses some routes. Option (d), 36, multiplies everything.
Tip: "and" (one step after another) means multiply; "or" (choose one route) means add.
Answer as per the official UPSC answer key.
Consider the following statements in respect of a rectangular sheet of length 20 cm and breadth 8 cm :
- 1. It is possible to cut the sheet exactly into 4 square sheets.
- 2. It is possible to cut the sheet into 10 triangular sheets of equal area.
Which of the above statements is/are correct?
Answer (c) & explanation
Both statements are correct (c). Step 1: the squares need not be equal. Cut two 8 × 8 squares from the 20 × 8 sheet. The leftover 4 × 8 strip makes two 4 × 4 squares. That is exactly 4 squares (1 is true). Step 2: cut the sheet into five 4 × 8 rectangles. Cut each along a diagonal to get two equal triangles. That gives 10 triangles of equal area (2 is true). Step 3: so options (a), (b) and (d) fail.
Tip: read "exactly 4 square sheets" carefully: it does not say equal squares. Don't add conditions the question does not state.
nothing says the four squares must be equal.
Answer as per the official UPSC answer key.
Consider the following statements :
- 1. Pursuant to the report of H.N. Sanyal Committee, the Contempt of Courts Act, 1971 was passed.
- 2. The Constitution of India empowers the Supreme Court and the High Courts to punish for contempt of themselves.
- 3. The Constitution of India defines Civil Contempt and Criminal Contempt.
- 4. In India, the Parliament is vested with the powers to make laws on Contempt of Court.
Which of the statements given above is/are correct?
Answer (b) & explanation
Statements 1, 2 and 4 are correct (b). Statement 1 is right: the H.N. Sanyal Committee (1963) led to the Contempt of Courts Act, 1971. Statement 2 is right: Article 129 and Article 215 make the Supreme Court and the High Courts courts of record, with power to punish contempt of themselves. Statement 4 is right: Parliament can make laws on contempt, under Entry 77 of the Union List and Entry 14 of the Concurrent List. Statement 3 is wrong: civil and criminal contempt are defined in the 1971 Act, not in the Constitution.
Notice the 2006 amendment, which made truth a defence if in the public interest. Contempt of court is also a ground for restricting free speech under Article 19(2).
statement 3. The Constitution gives the power; the Act gives the definitions.
Answer as per the official UPSC answer key.
With reference to “Gucchi” sometimes mentioned in the news, consider the following statements :
- 1. It is a fungus.
- 2. It grows in some Himalayan forest areas.
- 3. It is commercially cultivated in the Himalayan foothills of north-eastern India.
Which of the statements given above is/are correct ?
Answer (c) & explanation
Statements 1 and 2 are correct (c). Statement 1 is right: gucchi is the morel mushroom, a fungus with a honeycomb-like cap. Statement 2 is right: it grows wild in the Himalayan forests of Jammu and Kashmir, Himachal Pradesh and Uttarakhand, usually in spring after snowmelt. Statement 3 is wrong: it is gathered from the wild, not commercially farmed in the north-eastern foothills. That scarcity is why it sells for ₹20,000–30,000 a kilogram or more.
Notice other high-value Himalayan forest products: keeda jadi (Cordyceps, the caterpillar fungus) and kutki. Notice too the GI tag culture: J&K's saffron and Himachal's Kala Zeera. Morels are part of the minor forest produce that supports hill communities.
Answer as per the official UPSC answer key.
With reference to the United Nations General Assembly, consider the following statements :
- 1. The UN General Assembly can grant observer status to the non-member States.
- 2. Inter-governmental organisations can seek observer status in the UN General Assembly.
- 3. Permanent Observers in the UN General Assembly can maintain missions at the UN headquarters.
Which of the statements given above are correct ?
Answer (d) & explanation
All three statements are correct (d). Statement 1 is right: the General Assembly can give observer status to non-member states; today these are the Holy See and Palestine, which was upgraded to non-member observer state in 2012. Statement 2 is right: intergovernmental organisations such as the European Union, the African Union and the Commonwealth can seek and hold observer status. Statement 3 is right: permanent observers may keep missions at the UN headquarters in New York. So options (a), (b) and (c) each miss one true line.
Notice the limits: observers can speak and take part in debates but cannot vote. Some NGOs and bodies, like the International Committee of the Red Cross, also hold observer status.
Answer as per the official UPSC answer key.
Two friends X and Y start running and they run together for 50 m in the same direction and reach a point. X turns right and runs 60 m, while Y turns left and runs 40 m. Then X turns left and runs 50 m and stops, while Y turns right and runs 50 m and then stops. How far are the two friends from each other now?
Answer (a) & explanation
They are 100 m apart (a). Step 1: say they first run 50 m North together. Step 2: X turns right (East) and runs 60 m. Y turns left (West) and runs 40 m. Now they are 60 + 40 = 100 m apart on an east-west line. Step 3: X turns left (North) and runs 50 m. Y turns right (also North) and runs 50 m. Both move the same distance in the same direction, so the gap stays 100 m. Options (b), (c) and (d) miss this.
Tip: draw a quick sketch. When two people move the same distance in the same direction, the distance between them does not change.
the first 50 m and the last 50 m are common to both, so ignore them.
Answer as per the official UPSC answer key.
Two Statements followed by four Conclusions are given below. You have to take the Statements to be true even if they seem to be at variance from the commonly known facts. Read all the Conclusions and then decide which of the given Conclusions logically follows/follow from the Statements, disregarding the commonly known facts :
Statement-1 : All pens are books.
Statement-2 : No chair is a pen.
Conclusion-I : All chairs are books.
Conclusion-II : Some chairs are pens.
Conclusion-III : All books are chairs.
Conclusion-IV : No chair is a book.
Which one of the following is correct?
Answer (d) & explanation
None of the conclusions follows (d). Step 1: draw pens inside books, and chairs outside pens. Step 2: chairs may overlap the part of books that is not pens, or may lie fully outside books. So "all chairs are books" (I) and "no chair is a book" (IV) are both only possible, not certain. Step 3: "some chairs are pens" (II) contradicts Statement-2. "All books are chairs" (III) cannot be true because pens are books but not chairs. So options (a), (b) and (c) fail.
Tip: draw the circles in more than one way. A conclusion follows only if it holds in every drawing.
'No chair is a pen' does not mean 'no chair is a book'. Books are bigger than pens.
Answer as per the official UPSC answer key.
A pie chart gives the expenditure on five different items A, B, C, D and E in a household. If B, C, D and E correspond to 90°, 50°, 45° and 75° respectively, then what is the percentage of expenditure on item A?
Answer (d) & explanation
Item A is 250/9 % (d). Step 1: a full pie is 360°. B + C + D + E = 90 + 50 + 45 + 75 = 260°. Step 2: so A gets 360 − 260 = 100°. Step 3: as a percentage: 100 ÷ 360 × 100 = 10000 ÷ 360 = 250/9 (about 27.8%). Options (a), (b) and (c) use wrong angles.
Tip: in pie charts, 1% = 3.6° and 1° = 5/18 %. So 100° = 500/18 = 250/9 %.
Answer as per the official UPSC answer key.
Gandikota canyon of South India was created by which one of the following rivers ?
Answer (c) & explanation
The Pennar created the Gandikota canyon (c). Gandikota, in Kadapa (YSR) district of Andhra Pradesh, is a deep gorge cut by the Pennar (Penna) river through the Erramala hills. It is called the "Grand Canyon of India", and a medieval fort stands on its rim. The Cauvery (a) flows through Karnataka and Tamil Nadu. The Manjira (b) is a tributary of the Godavari. The Tungabhadra (d) is a tributary of the Krishna, flowing past Hampi.
Notice that the Pennar rises in the Nandi Hills of Karnataka and enters the Bay of Bengal near Nellore. India's other canyons include the Marble Rocks gorge of the Narmada at Bhedaghat.
Answer as per the official UPSC answer key.
With reference to Indian history, consider the following statements :
- 1. The first Mongol invasion of India happened during the reign of Jalal-ud-din Khalji.
- 2. During the reign of Ala-ud-din Khalji, one Mongol assault marched up to Delhi and besieged the city.
- 3. Muhammad-bin-Tughlaq temporarily lost portions of north-west of his kingdom to Mongols.
Which of the statements given above is/are correct ?
Answer (b) & explanation
Only statement 2 is correct (b). Statement 2 is right: under Alauddin Khalji, the Mongol leader Targhi camped outside Delhi and besieged it in 1303, while the Sultan's army was away; earlier, Qutlugh Khwaja had also reached Delhi in 1299. Statement 1 is wrong: the Mongols first reached India's frontier in 1221, under Iltutmish, when Chingiz Khan chased Jalal-ud-din Mangbarni to the Indus. Statement 3 is treated as wrong: Tarmashirin's raid in about 1327 reached near Delhi under Muhammad bin Tughlaq, but he went back without holding territory.
Notice that the Mongol threat shaped Alauddin's reforms: a large standing army, market control to pay it cheaply, and the branding of horses (dagh) and descriptive rolls of soldiers (huliya).
The name Jalal-ud-din is a double trap. It points to the Khalji sultan, but the Jalal-ud-din in the 1221 story is the prince Chingiz was chasing.
Answer as per the official UPSC answer key.
With reference to Indian laws about wildlife protection, consider the following statements :
- 1. Wild animals are the sole property of the government.
- 2. When a wild animal is declared protected, such animal is entitled for equal protection whether it is found in protected areas or outside.
- 3. Apprehension of a protected wild animal becoming a danger to human life is sufficient ground for its capture or killing.
Which of the statements given above is/are correct ?
Answer (b) & explanation
Only statement 2 is correct (b). Statement 2 is right: once a species is listed under the Wild Life (Protection) Act, 1972, it is protected everywhere, inside or outside a national park or sanctuary. Statement 1 is wrong: Section 39 makes certain wild animals, such as those hunted or found dead, government property, but not every wild animal in every case, so "sole property" is too wide. Statement 3 is wrong: only the Chief Wildlife Warden can allow a protected animal to be captured or killed, and only when it has become dangerous to human life; mere fear is not enough.
Notice the 2022 amendment, which cut the schedules to four and brought CITES listings into Indian law. Man-animal conflict cases test this rule often.
"sole property" is the over-strong word.
Answer as per the official UPSC answer key.
In a tournament of Chess having 150 entrants, a player is eliminated whenever he loses a match. It is given that no match results in a tie/draw. How many matches are played in the entire tournament?
Answer (c) & explanation
149 matches are played (c). Step 1: every match has a loser, and every loser is knocked out. No match is drawn. Step 2: in the end only one champion is left. So 150 − 1 = 149 players must be knocked out. Step 3: one match per knocked-out player means 149 matches. Option (b), 150, counts the champion too. Options (a) and (d) are off by one in other ways.
Tip: in any knockout tournament with n players, the number of matches is n − 1, whatever the number of rounds or byes.
Answer as per the official UPSC answer key.
Consider the Question and two Statements given below :
Question: What is the age of Manisha?
Statement-1 : Manisha is 24 years younger than her mother.
Statement-2 : 5 years later, the ages of Manisha and her mother will be in the ratio 3 : 5.
Which one of the following is correct in respect of the Question and the Statements?
Answer (c) & explanation
Both statements together are sufficient (c). Step 1: Statement-1 alone says Manisha is 24 years younger than her mother. That is one link between two unknowns, so it is not enough. Step 2: Statement-2 alone gives a future ratio, again with two unknowns. Not enough. Step 3: together: if Manisha is m, her mother is m + 24. In 5 years: (m + 5) ÷ (m + 29) = 3 ÷ 5. So 5m + 25 = 3m + 87, and m = 31. Options (a), (b) and (d) fail.
Tip: two unknowns need two independent facts. Each statement here gives one, so together they suffice.
Answer as per the official UPSC answer key.
"Rapid Financing Instrument" and "Rapid Credit Facility" are related to the provisions of lending by which one of the following ?
Answer (b) & explanation
Both are IMF lending windows (b). The Rapid Financing Instrument (RFI) and the Rapid Credit Facility (RCF) are emergency windows of the International Monetary Fund for countries facing an urgent balance of payments need, such as after a natural disaster, a conflict or the COVID-19 shock. The RFI is open to all members. The RCF gives concessional (zero or low-interest) loans to low-income countries through the Poverty Reduction and Growth Trust. Neither needs a full IMF programme. The ADB (a), UNEP FI (c) and World Bank (d) do not run these facilities.
Notice the IMF's other tools: the Extended Fund Facility and Stand-By Arrangements, and Special Drawing Rights (SDRs). India took an IMF loan in 1991.
"Financing" and "Credit" sound like a development bank. Quick, short-term BoP help is the IMF's job.
Answer as per the official UPSC answer key.
Which one of the following is the context in which the term “qubit” is mentioned ?
Answer (b) & explanation
A qubit relates to quantum computing (b). A qubit, or quantum bit, is the basic unit of quantum computing. An ordinary bit is either 0 or 1. Through superposition, a qubit can be 0 and 1 at once, and qubits can be entangled, so their states are linked. This lets quantum computers solve some problems, such as cryptography and molecular modelling, far faster. It is not a term from cloud services (a), visible light communication (c) such as Li-Fi, or wireless technology (d).
Notice India's National Quantum Mission (2023), with about ₹6,000 crore, which aims to build 50–1,000 qubit machines within eight years. 2025 was the UN's International Year of Quantum Science and Technology.
Answer as per the official UPSC answer key.
In India, which one of the following is responsible for maintaining price stability by controlling inflation ?
Answer (d) & explanation
The Reserve Bank of India controls inflation (d). The RBI Act, 1934, amended in 2016, says the primary objective of monetary policy is price stability while keeping growth in mind. The government sets a CPI inflation target of 4%, with a band of 2–6%, and the six-member Monetary Policy Committee sets the repo rate to meet it. Option (a) is wrong: the Department of Consumer Affairs tracks prices of essentials and runs consumer protection. Option (b) is wrong: the Expenditure Management Commission (2014) only advised on government spending. Option (c) is wrong: the FSDC, chaired by the Finance Minister, looks after financial stability, not inflation.
Notice that if inflation stays outside the band for three quarters in a row, the RBI must explain it in writing to the government.
Answer as per the official UPSC answer key.