UPSC Prelims PYQs with explanations
Real questions from official papers, mapped to syllabus topics. Attempt each one; the answer and the reason appear instantly.
In a row 'A' is in the 11th position from the left and 'B' is in the 10th position from the right. If 'A' and 'B' interchange, then 'A' becomes 18th from the left. How many persons are there in the row other than 'A' and 'B' ?
Answer (c) & explanation
There are 25 other people (c). Step 1: A is 11th from the left and B is 10th from the right. When they swap, A moves into B's old seat and becomes 18th from the left. Step 2: so B's old seat is 18th from the left and 10th from the right. Step 3: total people = 18 + 10 − 1 = 27. We subtract 1 because that seat was counted twice. Step 4: people other than A and B = 27 − 2 = 25. Options (a), (b) and (d) miss one of these steps.
Tip: total in a row = position from left + position from right − 1, for the same person or seat. Read the last line carefully: "other than A and B".
the question asks for people other than A and B.
Answer as per the official UPSC answer key.
Which of the following adds/add carbon dioxide to the carbon cycle on the planet Earth?
- 1. Volcanic action
- 2. Respiration
- 3. Photosynthesis
- 4. Decay of organic matter
Select the correct answer using the code given below.
Answer (c) & explanation
Volcanic action releases CO₂ stored in the Earth (1 correct). Respiration by plants, animals and microbes releases CO₂ (2 correct), and so does the decay of organic matter (4 correct). Photosynthesis does the opposite: it takes CO₂ out of the air and locks the carbon into plant matter, so options (a) and (d) fail.
On top of these natural flows, burning fossil fuels and clearing forests add extra carbon and drive climate change. Notice how this links biology (respiration and photosynthesis), geography (volcanoes) and environment (carbon sinks such as forests and oceans) in one cycle.
Answer as per the official UPSC answer key.
What is the correct sequence of occurrence of the following cities in South-East Asia as one proceeds from south to north?
- 1. Bangkok
- 2. Hanoi
- 3. Jakarta
- 4. Singapore
Select the correct answer using the code given below.
Answer (c) & explanation
Use latitudes. Jakarta (about 6° S) lies south of the equator. Singapore is at about 1° N, Bangkok about 14° N and Hanoi about 21° N. So from south to north the order is Jakarta–Singapore–Bangkok–Hanoi, that is 3-4-1-2 (c). Options (a) and (d) start with Singapore, ignoring that Jakarta is south of the equator, and (b) puts Hanoi too early.
Hanoi lies in northern Vietnam, close to China, while Ho Chi Minh City is in the south. Notice how a rough latitude for each capital turns map-sequence questions into simple arithmetic.
Answer as per the official UPSC answer key.
With reference to India’s culture and tradition, what is ‘Kalaripayattu’?
Answer (d) & explanation
Kalaripayattu is an ancient martial art and a living tradition of Kerala and nearby parts of South India (d). It is practised in a training pit called the kalari and covers footwork, kicks, weapons such as the flexible urumi sword, and healing massage. It is not a Shaiva Bhakti cult (a) or a bronze craft (b). The Malabar dance-drama in option (c) describes Theyyam or Kathakali.
Kathakali dancers draw on Kalari training for body control. Notice how martial arts, dance and traditional medicine (Ayurvedic massage) blend into one cultural world in Kerala.
Answer as per the official UPSC answer key.
Read the passage
Climate change poses potentially devastating effects on India’s agriculture. While the overall parameters of climate change are increasingly accepted — a 1°C average temperature increase over the next 30 years, sea level rise of less than 10 cm in the same period, and regional monsoon variations and corresponding droughts — the impacts in India are likely to be quite site and crop specific. Some crops may respond favourably to the changing conditions, others may not. This emphasizes the need to promote agricultural research and create maximum flexibility in the system to permit adaptations.
The key ingredient for “drought proofing” is the managed recharge of aquifers. To ensure continued yields of important staple crops (e.g. wheat), it may also be necessary to shift the locations where these crops are grown, in response to temperature changes as well as to water availability. The latter will be a key factor in making long term investment decisions.
For example, water runoff from the Himalayas is predicted to increase over the next 30 years as glaciers melt, but then decline substantially thereafter. It will be critical to provide incentives to plan for these large-scale shifts in agro-ecological conditions.
India needs to make long term investment in research and development in agriculture. India is likely to experience changed weather patterns in future.
According to the passage, why is it important to promote agricultural research in India ?
Answer (c) & explanation
Research is needed for wider adaptability of crops (c). Step 1: find the reason. Climate impacts are "site and crop specific"; some crops may do well and others not. "This emphasizes the need to promote agricultural research and create maximum flexibility in the system to permit adaptations." Step 2: test the others. Option (a) is wrong: the passage does not link research to predicting monsoons. Option (b) is wrong: long-term investment is linked to water availability, not to research's purpose. Option (d) is wrong: aquifer recharge is for drought-proofing, a separate point.
Tip: the answer usually sits in the same sentence as the key word of the question, here "research". Do not borrow ideas from other paragraphs.
Answer as per the official UPSC answer key.
A bell rings every 18 minutes. A second bell rings every 24 minutes. A third bell rings every 32 minutes. If all the three bells ring at the same time at 8 o'clock in the morning, at what other time will they all ring together?
Answer (b) & explanation
They ring together again at 12:48 (b). Step 1: find the LCM of 18, 24 and 32. Break them into factors: 18 = 2 × 3 × 3; 24 = 2 × 2 × 2 × 3; 32 = 2 × 2 × 2 × 2 × 2. Step 2: take the highest power of each: five 2s (32) and two 3s (9). LCM = 32 × 9 = 288 minutes. Step 3: 288 minutes = 4 hours 48 minutes. 8:00 + 4:48 = 12:48. Options (a), (c) and (d) are a few minutes off.
Tip: "ring together again" always means LCM. Turn the minutes into hours and minutes before adding to the start time.
Answer as per the official UPSC answer key.
A, B, C, D, E, F are members of a family. They are engineer, stenographer, doctor, draughtsman, lawyer and judge (not in order). A, the engineer is married to the lady stenographer. The judge is married to the lawyer. F, the draughtsman is the son of B and brother of E. C, the lawyer is the daughter-in-law of D. E is the unmarried doctor. D is the grandmother of F. There are two married couples in the family.
What is the profession of B ?
Answer (a) & explanation
B is the judge (a). Step 1: list known jobs. A is the engineer, C the lawyer, E the doctor and F the draughtsman. That leaves stenographer and judge for B and D. Step 2: the judge is married to the lawyer, C. C is the daughter-in-law of D, so D cannot be C's husband. So D is not the judge, and B is the judge. Step 3: D is then the lady stenographer, married to A. This fits: D is F's grandmother, and B, F's father, is D's son. Options (b), (c) and (d) fail.
Tip: in family puzzles, first fill in the direct clues, then use relationships like "daughter-in-law" to rule out who can be married to whom.
Answer as per the official UPSC answer key.
The terms 'Marginal Standing Facility Rate' and 'Net Demand and Time Liabilities', sometimes appearing in news, are used in relation to
Answer (a) & explanation
Both terms belong to banking operations (a). The Marginal Standing Facility (2011) lets banks borrow overnight from the RBI in an emergency against government securities, at a rate above the repo rate; it forms the ceiling of the policy corridor. Net Demand and Time Liabilities are a bank's deposits and certain other liabilities; the CRR and SLR are calculated as a share of NDTL. The other options are unrelated fields.
The floor of the corridor is now the Standing Deposit Facility (2022). Notice how these tools let the RBI keep the overnight call rate close to the repo rate.
Answer as per the official UPSC answer key.
Which one of the following is the process involved in photosynthesis?
Answer (b) & explanation
Photosynthesis captures light energy (free energy) and stores it as chemical potential energy in glucose made from carbon dioxide and water, releasing oxygen (b). Option (a) runs the wrong way: releasing stored energy happens in respiration. Options (c) and (d), oxidising food to give CO₂ and water and taking in oxygen, both describe respiration.
Photosynthesis happens in chloroplasts: the light reactions split water and release oxygen, and the dark reactions (Calvin cycle) fix carbon. Notice how the two processes mirror each other and together keep the oxygen and carbon cycles in balance.
Answer as per the official UPSC answer key.
There is some concern regarding the nanoparticles of some chemical elements that are used by the industry in the manufacture of various products. Why?
- 1. They can accumulate in the environment, and contaminate water and soil.
- 2. They can enter the food chains.
- 3. They can trigger the production of free radicals.
Select the correct answer using the code given below.
Answer (d) & explanation
All three are real concerns (d). Because they are so tiny, nanoparticles of silver, titanium dioxide and zinc oxide pass easily into soil, water and living cells, so they can accumulate and contaminate the environment (1). They can move up food chains (2). They can also trigger free radicals that cause oxidative damage to cells (3).
Their small size gives them a huge surface area, which makes them useful in sunscreens, medicines and electronics but also more reactive. Notice how the same property that makes a technology useful can make it risky, the core idea of the precautionary principle.
Answer as per the official UPSC answer key.
Six identical cards are placed on a table. Each card has number '1' marked on one side and number '2' marked on its other side. All the six cards are placed in such a manner that the number '1' is on the upper side. In one try, exactly four (neither more nor less) cards are turned upside down. In how many least number of tries can the cards be turned upside down such that all the six cards show number '2' on the upper side ?
Answer (a) & explanation
Three tries are enough (a). Step 1: each card starts on 1 and must end on 2, so each card must be turned an odd number of times. Step 2: can two tries work? In two tries a card is turned 0, 1 or 2 times. The only odd choice is exactly once, so all six cards would be turned once: 6 turns in total. But two tries always make exactly 4 + 4 = 8 turns. That is impossible. Step 3: three tries work. Turn cards 1, 4, 5, 6; then 2, 4, 5, 6; then 3, 4, 5, 6. Cards 1, 2, 3 turn once and cards 4, 5, 6 turn three times. All now show 2. Options (b), (c) and (d) are not the least number.
Tip: in flipping puzzles, think about odd and even counts; it rules out small answers quickly.
Answer as per the official UPSC answer key.
Read the passage
Net profits are only 2·2% of their total assets for central public sector undertakings, lower than for the private corporate sector. While the public sector or the State-led entrepreneurship played an important role in triggering India’s industrialization, our evolving development needs, comparatively less-than-satisfactory performance of the public sector enterprises, the maturing of our private sector, a much larger social base now available for expanding entrepreneurship and the growing institutional capabilities to enforce competition policies would suggest that the time has come to review the role of public sector.
What should the portfolio composition of the government be ? It should not remain static all times. The airline industry works well as a purely private affair. At the opposite end, rural roads, whose sparse traffic makes tolling unviable, have to be on the balance-sheet of the State. If the government did not own rural roads, they would not exist. Similarly, public health capital in our towns and cities will need to come from the public sector. Equally, preservation and improvement of forest cover will have to be a new priority for the public sector assets.
Take the example of steel. With near-zero tariffs, India is a globally competitive market for the metal. Indian firms export steel into the global market, which demonstrates there is no gap in technology. Indian companies are buying up global steel companies, which shows there is no gap in capital availability. Under these conditions, private ownership works best.
Private ownership is clearly desirable in regulated industries, ranging from finance to infrastructure, where a government agency performs the function of regulation and multiple competing firms are located in the private sector. Here, the simple and clean solution — government as the umpire and the private sector as the players is what works best. In many of these industries, we have a legacy of government ownership, where productivity tends to be lower, fear of bankruptcy is absent, and the risk of asking for money from the tax payer is ever present. There is also the conflict of interest between government as an owner and as the regulator. The formulation and implementation of competition policy will be more vigorous and fair if government companies are out of action.
The portfolio composition of the government refers to
Answer (c) & explanation
Portfolio composition means the mix of government investment across sectors (c). Step 1: see how the passage uses the term. Right after asking "What should the portfolio composition of the government be?", it discusses which sectors the State should own: airlines private, rural roads public, public health public, forests public, steel private. So the term means the mix of sectors in which government invests. Step 2: test the others. Option (a) is wrong: asset quality is not discussed. Option (b) is wrong: liquid assets are not mentioned. Option (d) is wrong: return on investment is not the point.
Tip: for a word-meaning question, read the examples that follow the term; they reveal its meaning in context.
Answer as per the official UPSC answer key.
Consider the following pairs :
- 1. Dampa Tiger Reserve : Mizoram
- 2. Gumti Wildlife Sanctuary : Sikkim
- 3. Saramati Peak : Nagaland
Which of the above pairs is/are correctly matched?
Answer (c) & explanation
Dampa Tiger Reserve is in Mizoram, on the Bangladesh border (1 correct). Saramati (about 3,840 m) is the highest peak of Nagaland, on the Myanmar border (3 correct). Pair 2 is wrong: Gumti Wildlife Sanctuary is in Tripura, not Sikkim, so options (b) and (d) fall away.
Gumti is named after the Gumti river, whose dam created the Dumbur lake. Sikkim's protected areas include Khangchendzonga National Park, India's first "mixed" World Heritage Site. Notice how UPSC mixes north-eastern states in pairs questions: placing each site on a mental map of the region is the surest defence.
Answer as per the official UPSC answer key.
In India, the problem of soil erosion is associated with which of the following?
- 1. Terrace cultivation
- 2. Deforestation
- 3. Tropical climate
Select the correct answer using the code given below.
Answer (b) & explanation
Deforestation strips away the plant cover whose roots hold soil, and is a major cause of erosion (2 correct). Terrace cultivation is a way to check erosion on slopes, not cause it, so statement 1 is wrong. UPSC's key does not count a tropical climate as a cause by itself, so the answer is (b).
Heavy rain can speed up erosion, but it does the damage mainly where cover has already been removed. Other conservation methods include contour ploughing, strip cropping, shelter belts and check dams. Notice how good farming practice, not climate alone, decides whether soil stays or goes.
Terracing is a remedy for soil erosion, not a cause of it.
Answer as per the official UPSC answer key.
Consider the following towns of India :
- 1. Bhadrachalam
- 2. Chanderi
- 3. Kancheepuram
- 4. Karnal
Which of the above are famous for the production of traditional sarees/fabric?
Answer (b) & explanation
Chanderi (Ashoknagar, Madhya Pradesh) weaves light, sheer silk-cotton saris with zari borders, and Kanchipuram (Tamil Nadu) is famous for heavy silk saris with temple borders. Both carry GI tags, so the answer is (b). Bhadrachalam in Telangana is known for its Rama temple on the Godavari, and Karnal in Haryana is an agricultural centre, home to the National Dairy Research Institute, so options with 1 or 4 fail.
Other famous weaves include Banarasi, Paithani, Pochampally ikat and Muga silk. Notice how handloom questions blend art and culture with geography and GI tags.
Answer as per the official UPSC answer key.
Read the passage
It is easy for the government to control State-owned companies through nods and winks. So what really needs to be done as a first step is to put petrol pricing on a transparent formula — if the price of crude is x and the exchange rate y, then every month or fortnight, the government announces a maximum price of petrol, which anybody can work out from the x and the y. The rule has to be worked out to make sure that the oil-marketing companies can, in general, cover their costs. This will mean that if one company can innovate and cut costs, it will make greater profits. Hence, firms will be more prone to innovate and be efficient under this system. Once the rule is announced, there should be no interference by the government. If this is done for a while, private companies will re-enter this market. And once a sufficient number of them are in the fray, we can remove the rule-based pricing and leave it truly to the market (subject to, of course, the usual regulations of anti-trust and other competition laws).
Consider the following statements :
According to the passage, an oil company can make greater profits, if a transparent formula for petrol pricing is announced every fortnight or month, by
- 1. promoting its sales.
- 2. undertaking innovation.
- 3. cutting costs.
- 4. selling its equity shares at higher prices.
Which of the statements given above is/are correct ?
Answer (b) & explanation
Innovation and cost-cutting raise profits (b). Step 1: find the sentence. "If one company can innovate and cut costs, it will make greater profits." That gives items 2 and 3. Step 2: test the others. Item 1 is wrong: promoting sales is never mentioned; the formula fixes a maximum price, so profit comes from efficiency, not selling more. Item 4 is wrong: share prices are not mentioned at all. So options (a), (c) and (d) fail.
Tip: in "according to the passage" questions, tick only what the text actually says. An item that sounds sensible in real business, like sales promotion, is still wrong if the passage does not mention it.
Answer as per the official UPSC answer key.
(Same graph as the question above.)
How much more average profit did A make in the year 2000 than in the year 1999 ?
Answer (d) & explanation
A made ₹2,000 more in 2000 (d). Step 1: read A's line on the graph. In 1999, A is at 4 thousand, that is ₹4,000. In 2000, A is at 6 thousand, that is ₹6,000. Step 2: difference = 6,000 − 4,000 = ₹2,000. Options (a), (b) and (c) are too small.
Tip: the graph is in thousands of rupees. A common slip is to read 6 − 4 = 2 and pick ₹200 (option a). Always multiply by the unit on the axis before answering. Also check you are reading the right line: A's line is the thick one, B's has dots.
Answer as per the official UPSC answer key.
Location of B is north of A and location of C is east of A. The distances AB and AC are 5 km and 12 km respectively. The shortest distance (in km) between the locations B and C is
Answer (b) & explanation
B and C are 13 km apart (b). Step 1: B is north of A and C is east of A. North and east are at a right angle, so A, B and C form a right-angled triangle with the corner at A. Step 2: use the right-angle rule (Pythagoras): square the two short sides and add. 5 × 5 + 12 × 12 = 25 + 144 = 169. Step 3: 13 × 13 = 169, so the straight distance BC = 13 km. Option (a) multiplies the sides. Option (c) adds them, which is the road distance through A. Option (d) subtracts them.
Tip: remember common triples: 3-4-5, 5-12-13, 8-15-17. They save time in CSAT direction questions.
Answer as per the official UPSC answer key.
If you walk through countryside, you are likely to see some birds stalking alongside the cattle to seize the insects disturbed by their movement through grasses. Which of the following is/are such bird/birds?
- 1. Painted Stork
- 2. Common Myna
- 3. Black-necked Crane
Select the correct answer using the code given below.
Answer (b) & explanation
The common myna walks beside grazing cattle and snaps up insects stirred up from the grass (b), as does the cattle egret. The painted stork is a wading bird that feeds on fish in shallow water, not beside cattle. The black-necked crane lives in high-altitude wetlands of Ladakh and Tibet and winters in places like Arunachal Pradesh and Bhutan, far from lowland fields.
This feeding pattern is a kind of commensalism: the bird benefits and the cattle are largely unaffected. Notice how everyday rural sights become ecology questions on species interactions.
Answer as per the official UPSC answer key.
The scientific view is that the increase in global temperature should not exceed 2°C above pre-industrial level. If the global temperature increases beyond 3°C above the pre-industrial level, what can be its possible impact/impacts on the world?
- 1. Terrestrial biosphere tends toward a net carbon source.
- 2. Widespread coral mortality will occur.
- 3. All the global wetlands will permanently disappear.
- 4. Cultivation of cereals will not be possible anywhere in the world.
Select the correct answer using the code given below.
Answer (b) & explanation
The IPCC's Fourth Assessment (2007) warned that above about 3°C of warming, the terrestrial biosphere would tend to become a net carbon source, releasing more carbon than it absorbs (1 correct), and that widespread coral mortality would occur (2 correct). Statements 3 and 4 use extreme words: "all" wetlands vanishing permanently and cereals failing "anywhere" go far beyond the science, so the answer is (b).
The Paris Agreement (2015) aims to keep warming well below 2°C and pursue 1.5°C. Notice how words like "all", "only" and "anywhere" are often UPSC's signal of a wrong statement.
"All ... permanently" and "anywhere in the world": absolute words like these give the wrong statements away.
Answer as per the official UPSC answer key.