UPSC Prelims PYQs with explanations
Real questions from official papers, mapped to syllabus topics. Attempt each one; the answer and the reason appear instantly.
(Same figures as the question above.)
Which one of the following disciplines has the highest ratio of males to females?
Answer (a) & explanation
Physics is correct (a). Step 1: work out men ÷ women for each subject. Physics: 32 ÷ 8 = 4. Mathematics: 28 ÷ 8 = 3.5. Step 2: Chemistry: 16 ÷ 22, which is less than 1 (more women than men). Economics: 24 ÷ 8 = 3. Step 3: the highest ratio is Physics (4). So (b), (c) and (d) fail.
Tip: a 'ratio of males to females' is men divided by women. When the number of women is the same in several subjects (8 here), simply compare the number of men. Physics has the most men among those, so it wins quickly.
Answer as per the official UPSC answer key.
The Chinese traveller Yuan Chwang (Hiuen Tsang) who visited India recorded the general conditions and culture of India at that time. In this context, which of the following statements is/are correct?
- 1. The roads and river-routes were completely immune from robbery.
- 2. As regards punishment for offences, ordeals by fire, water and poison were the instruments for determining the innocence or guilt of a person.
- 3. The tradesmen had to pay duties at ferries and barrier stations.
Select the correct answer using the codes given below.
Answer (b) & explanation
Statements 2 and 3 are correct (b). Xuanzang (Hiuen Tsang) visited India in Harsha's time (about 630–645 CE). He records trials by ordeal, by fire, water, poison and weighing, to decide guilt or innocence (2), and duties at ferries and barrier stations paid by traders (3). Statement 1 is wrong: he was himself robbed more than once on his travels, so roads were not immune from robbery. So (a), (c) and (d) fail.
Notice his other records: he studied at Nalanda, attended Harsha's assemblies at Kannauj and Prayag, and wrote the 'Si-Yu-Ki' (Records of the Western World). Earlier, Fa-Hien visited under Chandragupta II, and later I-Tsing. Trap: 'completely immune' is an absolute claim his own story disproves.
Answer as per the official UPSC answer key.
The balance of payments of a country is a systematic record of
Answer (a) & explanation
Option (a) is correct. The balance of payments is a systematic record of all economic transactions between a country's residents and the rest of the world over a period, usually a year. It covers the current account, with trade in goods and services, income and transfers such as remittances, and the capital and financial account, with FDI, portfolio flows, loans and changes in reserves. (b), (c) and (d) are wrong because each describes only a part of the BoP: exports alone, government transactions alone or capital movements alone.
Notice India's pattern: a large merchandise trade deficit, offset by strong services exports (about US$387 billion in 2024–25) and remittances (about US$135 billion, the world's highest), keeps the current account deficit small. Trap: the stem's 'import and export' wording means all transactions, not goods only.
Answer as per the official UPSC answer key.
Consider the following liquid assets :
- 1. Demand deposits with the banks
- 2. Time deposits with the banks
- 3. Savings deposits with the banks
- 4. Currency
The correct sequence of these assets in the decreasing order of liquidity is
Answer (d) & explanation
The order 4–1–3–2 is correct (d). Currency is the most liquid asset, since it can be spent at once (4). Demand deposits in current accounts can be withdrawn at any time by cheque or transfer (1). Savings deposits are also withdrawable but have some limits on transactions (3). Time deposits (fixed deposits) are locked in for a period and carry penalties for early withdrawal, so they are the least liquid (2). (a), (b) and (c) give the wrong order.
Notice the money measures: M1 = currency with the public + demand deposits + other deposits with RBI; M3 (broad money) adds time deposits. Savings deposits are counted as demand deposits in M1. The more liquid the asset, the lower its interest. Trap: (b) puts demand deposits last.
Answer as per the official UPSC answer key.
Disguised unemployment generally means
Answer (c) & explanation
Marginal productivity of labour is zero is correct (c). In disguised unemployment, more people work on a job, often a family farm, than are actually needed. If some of them are removed, total output does not fall, so their marginal productivity is zero. They appear employed but are effectively surplus. (a) is wrong: it describes open unemployment. (b) is wrong: lack of alternatives may explain it but does not define it. (d) is wrong: low productivity is not the same as zero marginal product.
Notice the theory: Arthur Lewis's dual-sector model (1954) argued that surplus farm labour could move to industry without reducing farm output. India still has about 46% of its workforce in agriculture, a sign of hidden underemployment. Other types: seasonal, structural, frictional and cyclical. Trap: 'low' productivity is not 'zero'.
Answer as per the official UPSC answer key.
Read the passage
Crude mineral oil comes out of the earth as a thick brown or black liquid with a strong smell. It is a complex mixture of many different substances, each with its own individual qualities. Most of them are combinations of hydrogen and carbon in varying proportions. Such hydrocarbons are also found in other forms such as bitumen, asphalt and natural gas. Mineral oil originates from the carcasses of tiny animals and from plants that live in the sea. Over millions of years, these dead creatures form large deposits under the sea-bed; and ocean currents cover them with a blanket of sand and silt. As this mineral hardens, it becomes sedimentary rock and effectively shuts out the oxygen, so preventing the complete decomposition of the marine deposits underneath. The layers of sedimentary rock become thicker and heavier. Their pressure produces heat, which transforms the tiny carcasses into crude oil in a process that is still going on today.
Mineral oil deposits under the sea do not get completely decomposed because they
Answer (b) & explanation
(b) is correct. Step 1: the passage says the sediment 'becomes sedimentary rock and effectively shuts out the oxygen, so preventing the complete decomposition' of the deposits. So they do not fully decompose because rock forms and keeps oxygen out. Step 2: (a) is wrong: ocean currents only cover the deposits with sand and silt; they do not keep washing them. Step 3: (c) is wrong: being made of hydrogen and carbon describes oil, not why decay stops. (d) is wrong: saline conditions are not given as the reason. So (a), (c) and (d) fail.
Tip: decomposition needs oxygen. When a passage says something 'shuts out the oxygen', it is explaining why decay stops.
Answer as per the official UPSC answer key.
In a garrison, there was food for 1000 soldiers for one month. After 10 days, 1000 more soldiers joined the garrison. How long would the soldiers be able to carry on with the remaining food?
Answer (d) & explanation
10 days is correct (d). Step 1: taking a month as 30 days, food is for 1,000 soldiers × 30 days. After 10 days, food is left for 1,000 soldiers for 20 days. Step 2: now 2,000 soldiers share it. Double the soldiers, half the time: 20 ÷ 2 = 10 days. Step 3: (b) 20 days ignores the new soldiers; (a) and (c) do not fit the numbers. So (a), (b) and (c) fail. Note: the answer assumes a 30-day month, the usual convention in such questions.
Tip: think in 'soldier-days': total food = soldiers × days. What is left (1,000 × 20 = 20,000 soldier-days) divided by the new number of soldiers (2,000) gives the days.
Answer as per the official UPSC answer key.
Consider the following :
- 1. Electromagnetic radiation
- 2. Geothermal energy
- 3. Gravitational force
- 4. Plate movements
- 5. Rotation of the earth
- 6. Revolution of the earth
Which of the above are responsible for bringing dynamic changes on the surface of the earth?
Answer (d) & explanation
All six are correct (d). The Earth's surface is shaped by exogenic forces driven by solar radiation (1) and gravity (3): weathering, running water, wind, glaciers and mass movement. Endogenic forces come from geothermal energy (2) and plate movements (4): mountain building, volcanoes and earthquakes. Rotation (5) sets wind and ocean-current patterns through the Coriolis force and drives tides with the Moon. Revolution (6) brings the seasons, which change weathering, rivers and glaciers. So (a), (b) and (c) leave out real factors.
Notice the frame: geomorphology sees landforms as a balance between endogenic building and exogenic wearing down. Gravity also drives landslides on young slopes such as the Himalaya. Trap: rotation and revolution seem astronomical, but they shape climate and so the surface.
Answer as per the official UPSC answer key.
Consider the following Bhakti Saints :
- 1. Dadu Dayal
- 2. Guru Nanak
- 3. Tyagaraja
Who among the above was/were preaching when the Lodi dynasty fell and Babur took over?
Answer (b) & explanation
Guru Nanak only is correct (b). Babur defeated Ibrahim Lodi at the First Battle of Panipat in 1526. Guru Nanak (1469–1539) was preaching then, and his verses in the Babarvani describe the suffering caused by Babur's invasion (2). Item 1 is wrong: Dadu Dayal was born in 1544, in the Sur–Mughal period, and preached in Akbar's time. Item 3 is wrong: Tyagaraja (1767–1847), the great Carnatic composer, lived three centuries later. So (a), (c) and (d) fail.
Notice the other saints of that time: Kabir (d. around 1518) and Chaitanya (1486–1534) overlapped with the late Lodis; Vallabhacharya and Mirabai were active too. Dadu founded the Dadu Panth in Rajasthan. Trap: placing saints on a timeline is the whole test.
Answer as per the official UPSC answer key.
Supply of money remaining the same when there is an increase in demand for money, there will be
Answer (b) & explanation
An increase in the rate of interest is correct (b). The rate of interest is the price of money. If the demand for money rises while the supply stays the same, money becomes scarcer and its price, the interest rate, rises, in line with Keynes's liquidity preference theory. (a) is wrong: a higher interest rate may later cool prices, but the direct result is a rate rise. (c) is the opposite. (d) is wrong: income and employment are not directly raised; higher rates may even slow investment.
Notice the policy link: the RBI manages liquidity so that the overnight call money rate stays near the repo rate. When demand for money spikes, as at advance-tax time each quarter, short-term rates jump. Trap: (a) describes a possible later effect, not the immediate one.
Answer as per the official UPSC answer key.
Directions for the following 4 (four) items: Read the following statements and answer the four items that follow:
Five cities P, Q, R, S and T are connected by different modes of transport as follows:
P and Q are connected by boat as well as rail.
S and R are connected by bus and boat.
Q and T are connected by air only.
P and R are connected by boat only.
T and R are connected by rail and bus.
Which mode of transport would help one to reach R starting from Q, but without changing the mode of transport?
Answer (a) & explanation
Boat is correct (a). Step 1: list the links. P–Q: boat, rail. S–R: bus, boat. Q–T: air. P–R: boat. T–R: rail, bus. Step 2: from Q, one route is Q → P → R. Q to P can be done by boat, and P to R is by boat only, so the whole trip works by boat. Step 3: the other route, Q → T → R, needs air to T and then rail or bus to R, so you must change. Rail (Q–P by rail) fails because P–R is boat only. Bus and air do not connect Q to R either. So (b), (c) and (d) fail.
Tip: write each link with its modes in a small list. Then follow one mode at a time from start to finish.
Answer as per the official UPSC answer key.
Read the passage
The miseries of the world cannot be cured by physical help only. Until man’s nature changes, his physical needs will always arise, and miseries will always be felt, and no amount of physical help will remove them completely. The only solution of the problem is to make mankind pure. Ignorance is the mother of evil and of all the misery we see. Let men have light, let them be pure and spiritually strong and educated; then alone will misery cease in the world. We may convert every house in the country into a charitable asylum, we may fill the land with hospitals, but human misery will continue until man’s character changes.
With reference to the passage, the following assumptions have been made :
- 1. The author gives primary importance to physical and material help in eradicating human misery.
- 2. Charitable homes, hospitals, etc. can remove human misery to a great extent.
Which of the assumptions is/are valid ?
Answer (d) & explanation
Neither assumption is valid (d). Step 1: assumption 1 says the author gives primary importance to physical help. The passage says misery 'cannot be cured by physical help only' and that the 'only solution' is to make mankind pure. So 1 is wrong. Step 2: assumption 2 says charitable homes and hospitals can remove misery to a great extent. The author says even if we fill the land with them, 'human misery will continue'. So 2 is wrong. Step 3: so (a), (b) and (c) fail.
Tip: when an author uses 'only' and 'then alone', he is ranking one solution above all others. Assumptions that put any other solution first go against him.
Answer as per the official UPSC answer key.
Directions: each item describes a situation and is followed by four possible responses. Indicate the response you find most appropriate. There is no penalty for wrong answers for these items. You are the head of your office. There are certain houses reserved for the allotment to the office staff and you have been given the discretion to do so. A set of rules for the allotment of the houses has been laid down by you and has been made public. Your personal secretary, who is very close to you, comes to you and pleads that as his father is seriously ill, he should be given priority in allotment of a house. The office secretariat that examined the request as per the rules turns down the request and recommends the procedure to be followed according to the rules. You do not want to annoy your personal secretary. In such circumstances, what would you do ?
Answer (a) & explanation
(a) and (c) are both correct (UPSC accepted both; no negative marking). Step 1: you made the allotment rules public, and your office has applied them and refused the request. Step 2: (c) agreeing with the office note shows you follow your own rules without favouritism. (a) explaining the decision to him personally is also fair and keeps a good working relationship. Step 3: (b) allotting the house to win his loyalty is favouritism. (d) sitting on the file avoids a decision and is poor administration.
Tip: for these interpersonal items, pick the response that is lawful, honest and fixes the real problem through proper channels. Avoid options that give in to pressure, show favouritism or dodge a decision.
Answer as per the official UPSC answer key.
Due to improper/indiscriminate disposal of old and used computers or their parts, which of the following are released into the environment as e-waste?
- 1. Beryllium
- 2. Cadmium
- 3. Chromium
- 4. Heptachlor
- 5. Mercury
- 6. Lead
- 7. Plutonium
Select the correct answer using the codes given below.
Answer (b) & explanation
Items 1, 2, 3, 5 and 6 are correct (b). Computers contain beryllium in connectors and motherboards (1), cadmium in batteries and chips (2), hexavalent chromium used against corrosion (3), mercury in switches and older flat screens (5), and lead in solder and old CRT glass (6). Item 4 is wrong: heptachlor is an organochlorine insecticide, not part of electronics. Item 7 is wrong: plutonium is a nuclear material and is not used in computers. So (a), (c) and (d) fail.
Notice India's rules: the E-Waste (Management) Rules, 2022 use Extended Producer Responsibility with tradable EPR certificates. India produced over 1.7 million tonnes of e-waste in 2023–24, and much is handled informally in places like Seelampur, Delhi. Trap: scary-sounding toxins are not all e-waste.
Answer as per the official UPSC answer key.
Consider the following statements :
- 1. Natural gas occurs in the Gondwana beds.
- 2. Mica occurs in abundance in Kodarma.
- 3. Dharwars are famous for petroleum.
Which of the statements given above is/are correct?
Answer (b) & explanation
Statement 2 only is correct (b). Koderma in Jharkhand, part of the Koderma–Giridih–Hazaribagh belt, is India's best-known mica region (2). Statement 1 is wrong: the Gondwana beds hold most of India's coal, not natural gas. Statement 3 is wrong: the ancient Dharwar rocks hold metallic minerals such as iron ore, manganese and gold (Kolar, Hutti), not petroleum. Petroleum and natural gas occur in much younger Tertiary sedimentary rocks, as in Assam, Gujarat, Bombay High and the KG basin. So (a), (c) and (d) fail.
Notice the twist: some coal-bed methane is extracted from Gondwana coal seams, as at Raniganj, but it is not 'natural gas in Gondwana beds' in the usual sense. India's mica output has fallen, and illegal mining has linked to child labour. Trap: rock-system ages decide which minerals they hold.
Answer as per the official UPSC answer key.
The efforts to detect the existence of Higgs boson particle have become frequent news in the recent past. What is/are the importance/importances of discovering this particle?
- 1. It will enable us to understand as to why elementary particles have mass.
- 2. It will enable us in the near future to develop the technology of transferring matter from one point to another without traversing the physical space between them.
- 3. It will enable us to create better fuels for nuclear fission.
Select the correct answer using the codes given below.
Answer (a) & explanation
Statement 1 only is correct (a). The Higgs boson, discovered at CERN's Large Hadron Collider in July 2012, confirmed the Higgs field, which explains why elementary particles have mass (1). Statement 2 is wrong: it has no link to teleporting matter. Statement 3 is wrong: it does not help make nuclear fuels. So (b), (c) and (d) fail.
Notice the Indian link: the particle is a boson, a class named after Satyendra Nath Bose. Peter Higgs and François Englert won the 2013 Nobel Prize in Physics. India became an associate member of CERN in 2017. The popular name 'God particle' comes from a book title, not from physics. Trap: dramatic applications are attached to basic science.
Answer as per the official UPSC answer key.
(Same information as the question above.)
Which game do B, C and D play?
Answer (b) & explanation
Hockey is correct (b). Step 1: from the lists, B plays football, cricket, hockey; C plays cricket, hockey, basketball; D plays football, basketball, hockey. Step 2: the only game all three share is hockey. Step 3: basketball is not played by B, cricket is not played by D, and football is not played by C. So (a), (c) and (d) fail.
Tip: to find a common game, write the three lists side by side and look for the item present in all of them. Here, A is the only one without hockey, so the other three must share it. Using the earlier answer ('A does not play hockey') gives this in seconds.
Answer as per the official UPSC answer key.
(Same figures as the question above.)
What percentage of all Psychology professors are females?
Answer (c) & explanation
60% is correct (c). Step 1: from Figure 1, Psychology has 4 men and 6 women, so 10 professors in all. Step 2: women's share = 6 ÷ 10 = 0.6. Step 3: as a percentage, 0.6 × 100 = 60%. (a) 40% is the share of men, a common trap. (b) and (d) do not match the figures. So (a), (b) and (d) fail.
Tip: percentage = part ÷ whole × 100. Make sure the 'whole' is the total of the group (men + women), not the number of men. When the total is 10, the percentage is simply the part × 10.
Answer as per the official UPSC answer key.
Consider the following :
- 1. Star tortoise
- 2. Monitor lizard
- 3. Pygmy hog
- 4. Spider monkey
Which of the above are naturally found in India?
Answer (a) & explanation
Items 1, 2 and 3 are correct (a). The Indian star tortoise lives in dry scrub of peninsular India and Sri Lanka (1). Monitor lizards, such as the Bengal monitor, are widespread in India (2). The pygmy hog, the world's smallest and rarest wild pig, survives in Manas National Park and nearby grasslands in Assam (3). Item 4 is wrong: spider monkeys live only in the tropical forests of Central and South America. So (b), (c) and (d) fail.
Notice the conservation side: the star tortoise is heavily smuggled for the pet trade and was moved to CITES Appendix I in 2019. The Pygmy Hog Conservation Programme has bred and released hogs since 1996. India's only apes are the hoolock gibbons. Trap: 'monkey' sounds Indian but this one is American.
Answer as per the official UPSC answer key.
The Reserve Bank of India regulates the commercial banks in matters of
- 1. liquidity of assets
- 2. branch expansion
- 3. merger of banks
- 4. winding-up of banks
Select the correct answer using the codes given below.
Answer (d) & explanation
All four are correct (d). Under the Banking Regulation Act, 1949, the RBI regulates banks' liquidity through the CRR and SLR (1), licenses and controls branch expansion (2), approves mergers and amalgamations, and can impose schemes on weak banks (3), and can apply for the winding up of a bank or place it under a moratorium (4). So options (a), (b) and (c) leave out real powers.
Notice the recent uses: the RBI-led rescue of Yes Bank (2020), the merger of Lakshmi Vilas Bank with DBS (2020), and the 2020 amendment bringing cooperative banks under fuller RBI supervision. Branch authorisation has since been liberalised for scheduled banks. Deposit insurance up to ₹5 lakh comes from DICGC. Trap: winding up seems a court matter, but RBI starts it.
Answer as per the official UPSC answer key.