UPSC Prelims PYQs with explanations
Real questions from official papers, mapped to syllabus topics. Attempt each one; the answer and the reason appear instantly.
How many different 5-letter words (with or without meaning) can be constructed using all the letters of the word 'DELHI' so that each word has to start with D and end with I?
Answer (d) & explanation
6 such words can be made (d). Step 1: the word must start with D and end with I. So the first and last letters are fixed. Step 2: the middle three places are filled by E, L and H. Step 3: three letters can be arranged in 3 × 2 × 1 = 6 ways: ELH, EHL, LEH, LHE, HEL, HLE. Option (a), 24, fixes only one end (4! = 24). Options (b) and (c) do not follow any rule.
Tip: fix the letters whose places are given, then arrange the rest. n different letters can be arranged in n! ways. 3! = 6, 4! = 24, 5! = 120.
Answer as per the official UPSC answer key.
With reference to the history of India, consider the following pairs :
- 1. Aurang — In-charge of treasury of the State
- 2. Banian — Indian agent of the East India Company
- 3. Mirasidar — Designated revenue payer to the State
Which of the pairs given above is/are correctly matched ?
Answer (b) & explanation
Pairs 2 and 3 are correct (b). Pair 1 is wrong because an aurang (Persian for "workshop") was a place where goods, usually cloth, were made or collected before export. It did not mean a treasury officer. Pair 2 is right because a banian was the Indian agent or broker of a Company merchant, handling trade, money and translation. Pair 3 is right because mirasidars in the Madras region held hereditary rights in village land and were treated as the revenue payers to the state under the ryotwari settlement.
Notice the related terms: gomastha, the Company's paid Indian agent who supervised weavers; dadni, cash advances to weavers; and dubash, an interpreter in Madras. Such terms often appear in questions on early Company trade.
Answer as per the official UPSC answer key.
In India, why are some nuclear reactors kept under “IAEA Safeguards” while others are not ?
Answer (b) & explanation
Some reactors use imported uranium, others domestic (b). After the 2008 India–US civil nuclear deal and the Nuclear Suppliers Group waiver, India separated its civilian and military facilities. Reactors fuelled by imported uranium (from Russia, Kazakhstan, Canada and others) are placed under IAEA safeguards, so suppliers can check the fuel is not used for weapons. Reactors on domestic uranium and the strategic programme stay outside. Option (a) is wrong because thorium is not the dividing line. Options (c) and (d) are wrong because all Indian power reactors are run by state-owned firms such as NPCIL.
Notice India's three-stage nuclear programme, planned by Homi Bhabha: PHWRs, then fast breeder reactors, then thorium reactors. India is not a member of the NPT.
Answer as per the official UPSC answer key.
“The crop is subtropical in nature. A hard frost is injurious to it. It requires at least 210 frost-free days and 50 to 100 centimeters of rainfall for its growth. A light well-drained soil capable of retaining moisture is ideally suited for the cultivation of the crop.” Which one of the following is that crop ?
Answer (a) & explanation
The crop is cotton (a). Cotton is a subtropical crop that needs high temperatures, at least 210 frost-free days, moderate rain of 50–100 cm, and bright, sunny weather at picking time. A hard frost damages it. It grows best on light, well-drained soil that holds moisture, such as the black (regur) soil of the Deccan. Jute (b) needs hot, humid weather and over 150 cm of rain in the deltas. Sugarcane (c) needs 75–150 cm of rain or irrigation. Tea (d) needs over 150 cm of rain on well-drained hill slopes.
Notice the top cotton States: Gujarat and Maharashtra. Bt cotton is India's only approved GM crop. Cotton is a kharif crop.
Answer as per the official UPSC answer key.
One page is torn from a booklet whose pages are numbered in the usual manner starting from the first page as 1. The sum of the numbers on the remaining pages is 195. The torn page contains which of the following numbers?
Answer (b) & explanation
The torn page has 7 and 8 (b). Step 1: find the total before tearing. 1 + 2 + … + 20 = 20 × 21 ÷ 2 = 210. 1 to 19 gives only 190, which is less than 195, so the booklet had 20 pages. Step 2: missing sum = 210 − 195 = 15. Step 3: a torn leaf has two consecutive numbers that add to 15: 7 + 8. Option (a), 5 + 6 = 11. Option (c), 9 + 10 = 19. Option (d), 11 + 12 = 23. None of these is 15.
Tip: use n(n + 1) ÷ 2 for the sum of 1 to n. Find the smallest total just above the given sum; the difference is the torn page.
Answer as per the official UPSC answer key.
Read the passage
Economic liberalization in India was shaped largely by the economic problems of the government than by the economic priorities of the people or by the long-term development objectives. Thus, there were limitations in conception and design which have been subsequently validated by experience. Jobless growth, persistent poverty and rising inequality have mounted as problems since economic liberalization began. And all these years later, four quiet crises confront the economy; agriculture, infrastructure, industrialization and education as constraints on the country’s future prospects. These problems must be resolved if economic growth has to be sustained and transformed into meaningful development.
With reference to the above passage, the following assumptions have been made :
- 1. India’s economy needs to be greatly integrated with global economy so as to create large number of jobs and to sustain its growth momentum.
- 2. Economic liberalization would cause large economic growth which would reduce poverty and create sufficient employment in the long run.
Which of the above assumptions is/are valid?
Answer (d) & explanation
Neither assumption is valid (d). Step 1: the passage blames liberalisation for "jobless growth, persistent poverty and rising inequality". Step 2: assumption 1 says India needs more integration with the global economy to create jobs. That praises integration, against the passage's tone. Step 3: assumption 2 says liberalisation will cut poverty and create jobs in the long run. That also praises it. Both go against the passage. So options (a), (b) and (c) fail.
Tip: check the author's attitude. If the passage is critical of a policy, statements praising that policy cannot be its assumptions.
Answer as per the official UPSC answer key.
If 1 litre of water weighs 1 kg, then how many cubic millimetres of water will weigh 0·1 gm?
Answer (c) & explanation
100 cubic millimetres of water weigh 0·1 gm (c). Step 1: 1 litre weighs 1 kg, so 1 ml weighs 1 g. And 1 ml = 1 cm³. Step 2: 1 cm = 10 mm, so 1 cm³ = 10 × 10 × 10 = 1000 mm³. So 1 g of water = 1000 mm³. Step 3: 0·1 g = 0·1 × 1000 = 100 mm³. Option (d), 1000, is the volume for 1 g. Options (a) and (b) fail.
Tip: water facts to remember: 1 ml = 1 cm³ = 1 g; 1 litre = 1000 cm³ = 1 kg. When converting cubic units, cube the length factor: (10)³ = 1000.
Answer as per the official UPSC answer key.
Wellesley established the Fort William College at Calcutta because
Answer (d) & explanation
Wellesley wanted to train British civilians for administration (d). Lord Wellesley set up Fort William College in Calcutta in 1800 to train young Company civil servants in Indian languages, law, history and customs, so they could govern better. The Court of Directors in London did not ask for it (a); they disliked its cost and set up their own East India College at Haileybury in 1806. Option (b) is wrong because reviving oriental learning was not its main purpose, though it helped. Option (c) is wrong because William Carey did teach Bengali and Sanskrit there, but that was a result, not the reason.
Notice its legacy: scholars like John Gilchrist helped develop modern Hindustani and Bengali prose. It closed in 1854.
Answer as per the official UPSC answer key.
Under the Kisan Credit Card scheme, short-term credit support is given to farmers for which of the following purposes ?
- 1. Working capital for maintenance of farm assets
- 2. Purchase of combine harvesters, tractors and mini trucks
- 3. Consumption requirements of farm households
- 4. Post-harvest expenses
- 5. Construction of family house and setting up of village cold storage facility
Select the correct answer using the code given below :
Answer (b) & explanation
Items 1, 3 and 4 are covered (b). The Kisan Credit Card scheme (1998) gives farmers a revolving short-term credit limit. It covers crop cultivation, post-harvest expenses (item 4), consumption needs of the farm household (item 3), and working capital for maintaining farm assets and allied work (item 1). Item 2 is wrong because tractors, harvesters and mini trucks are long-term assets financed by term loans. Item 5 is wrong because a family house and a village cold storage are also long-term investments, not short-term credit.
Notice the interest subvention scheme: KCC loans up to ₹3 lakh carry a low rate, with an extra rebate for prompt repayment. KCC was extended to animal husbandry and fisheries in 2018–19.
Answer as per the official UPSC answer key.
Consider the following statements :
- 1. 36% of India’s districts are classified as “overexploited” or “critical” by the Central Ground Water Authority (CGWA).
- 2. CGWA was formed under the Environment (Protection) Act.
- 3. India has the largest area under groundwater irrigation in the world.
Which of the statements given above is/are correct ?
Answer (b) & explanation
Statements 2 and 3 are correct (b). Statement 1 is wrong per the key: assessments by the Central Ground Water Board classify blocks, not whole districts, as over-exploited or critical, and the figures did not match 36% of districts by the CGWA. Statement 2 is right: the Central Ground Water Authority was set up in 1997 under Section 3(3) of the Environment (Protection) Act, 1986, to regulate groundwater use. Statement 3 is right: India uses more groundwater than any other country and has the largest area irrigated by it.
Notice Atal Bhujal Yojana (2019), which works on community groundwater management in seven States. Punjab, Haryana and Rajasthan have the worst over-extraction.
CGWB and CGWA again. The Board assesses; the Authority regulates.
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Answer as per the official UPSC answer key.
Read the passage
Our urban bodies cannot possibly ensure sustainable delivery of water in our cities unless financing mechanisms are put in place. Water delivery requires heavy investment in collecting it from a natural source, treating it to make it potable, and laying a distribution network of pipes for delivery to the users. It also requires investments in sewerage infrastructure and sewage treatment plants so that the sewers can carry the wastewater to these plants to ensure that no untreated sewage is discharged back into natural water bodies. If our cities were rich enough to meet the entire cost, water could be delivered free. They are not.
With reference to the above passage, the following assumptions have been made :
- 1. Rich cities only can ensure sustainable delivery of water.
- 2. Sustainable delivery of water in cities means much more than supplying water to households.
Which of the above assumptions is/are valid?
Answer (b) & explanation
Only assumption 2 is valid (b). Step 1: the passage says water delivery includes treatment, pipes, sewers and sewage plants. So sustainable delivery means much more than supplying water to homes (2). Step 2: assumption 1 says only rich cities can do this. But the passage says poorer cities can also deliver with "financing mechanisms". So 1 fails. Step 3: so options (a), (c) and (d) fail.
Tip: "only" claims fail if the passage shows another way. India's AMRUT 2.0 mission funds water supply and sewerage in cities that cannot pay alone.
Answer as per the official UPSC answer key.
A sum of ₹ 2,500 is distributed among X, Y and Z in the ratio 1/2 : 3/4 : 5/6. What is the difference between the maximum share and the minimum share?
Answer (c) & explanation
The difference is ₹ 400 (c). Step 1: clear the fractions by multiplying each by 12 (the LCM of 2, 4 and 6): ½ × 12 = 6, ¾ × 12 = 9, ⅚ × 12 = 10. So the ratio is 6 : 9 : 10. Step 2: total parts = 25. One part = 2500 ÷ 25 = ₹ 100. Step 3: maximum − minimum = (10 − 6) × 100 = ₹ 400. So X gets ₹ 600, Y ₹ 900 and Z ₹ 1000. Options (a), (b) and (d) do not fit.
Tip: to simplify a ratio of fractions, multiply all terms by the LCM of the denominators. Then share the total by parts.
Answer as per the official UPSC answer key.
Consider the following pairs :
| International agreement / set-up | Subject
| 1. Alma-Ata Declaration | Healthcare of the people
| 2. Hague Convention | Biological and chemical weapons
| 3. Talanoa Dialogue | Global climate change
| 4. Under2 Coalition | Child rights
Which of the pairs given above is/are correctly matched ?
Answer (c) & explanation
Pairs 1 and 3 are correct (c). The Alma-Ata Declaration (1978), from a WHO–UNICEF conference in Kazakhstan, set the goal of primary health care for all (1). The Talanoa Dialogue (2018), named after a Fijian word for open, inclusive talk, was a UNFCCC stock-take of climate action (3). Pair 2 is wrong because biological and chemical weapons are covered by the Biological Weapons Convention (1972) and the Chemical Weapons Convention (1993), not a "Hague Convention". Pair 4 is wrong because the Under2 Coalition is a group of state and regional governments working to keep warming under 2°C, not on child rights.
Notice the Astana Declaration (2018), which renewed Alma-Ata's goal. India's Ayushman Arogya Mandirs (health and wellness centres) carry the primary health care idea forward.
"Under2" sounds like "under 2 years", but it means keeping warming under 2°C.
Answer as per the official UPSC answer key.
What is the importance of using Pneumococcal Conjugate Vaccines in India ?
- 1. These vaccines are effective against pneumonia as well as meningitis and sepsis.
- 2. Dependence on antibiotics that are not effective against drug-resistant bacteria can be reduced.
- 3. These vaccines have no side effects and cause no allergic reactions.
Select the correct answer using the code given below :
Answer (b) & explanation
Statements 1 and 2 are correct (b). Pneumococcal Conjugate Vaccine (PCV) protects against Streptococcus pneumoniae, a bacterium that causes pneumonia, meningitis and sepsis (1). Pneumonia is a leading killer of young children in India. Statement 2 is right because fewer infections mean less antibiotic use, which slows the spread of drug-resistant bacteria. Statement 3 is wrong because, like every vaccine, PCV can cause side effects such as fever or swelling, and rare allergic reactions.
PCV was added to the Universal Immunisation Programme in 2017 and expanded across India in 2021. Notice India's own PCV, Pneumosil, made by the Serum Institute and approved in 2020. The U-WIN portal (2024) now records every vaccination digitally.
Answer as per the official UPSC answer key.
Which of the following are the most likely places to find the musk deer in its natural habitat ?
- 1. Askot Wildlife Sanctuary
- 2. Gangotri National Park
- 3. Kishanpur Wildlife Sanctuary
- 4. Manas National Park
Select the correct answer using the code given below :
Answer (a) & explanation
Askot and Gangotri are the likely homes of musk deer (a). The Himalayan musk deer lives in high alpine forests and scrub, usually above 2,500 metres. Item 1 is right: Askot Wildlife Sanctuary in Pithoragarh, Uttarakhand, was set up partly to protect musk deer. Item 2 is right: Gangotri National Park lies in the high Garhwal Himalaya. Item 3 is wrong: Kishanpur is in the Terai of Uttar Pradesh, part of Dudhwa Tiger Reserve, too low and warm. Item 4 is wrong: Manas is in the lowland Assam plains.
Notice that males are poached for musk, a gland used in perfume and medicine; the species is Endangered and in Schedule I. The alpine musk deer is the state animal of Uttarakhand.
Answer as per the official UPSC answer key.
Read the passage
Asset allocation is the most important investment decision we will ever make, and sadly, most of us do not give that decision the importance it deserves. We are adamant about seeking predictability with our future. We tend to think of investing in risky assets as extremely volatile and value eroding. We also dislike fluctuating returns and the loss of control of investment. We think our money is best left idle, unproductive but safe. There is no asset that is risk-free. We could lose our jobs, our homes can lose value, our banks can go bankrupt, our bonds can default, the government can collapse and companies we chose fondly may cease to exist. But we cannot live life assuming that all these extreme events are waiting to happen, and all at the same time. All these extreme forms of risks we know will not manifest at the same time.
Which one of the following statements best implies the suggestion given by the author of the passage?
Answer (a) & explanation
The author suggests spreading wealth across different assets to cut risk (a). Step 1: the passage says no asset is risk-free, but all risks "will not manifest at the same time". So holding many kinds of assets means losses in one are offset by gains in another. That is diversification, option (a). Step 2: option (d), investing is risky, just restates a fact; it is not a suggestion. Step 3: option (b) makes risk-taking a necessary part of personality, which overstates. Option (c), hiring an asset manager, is not mentioned.
Tip: "don't put all your eggs in one basket" is the core idea. When asked for a suggestion, pick an action that solves the problem the passage describes.
Answer as per the official UPSC answer key.
Three Statements S1, S2 and S3 are given below followed by a Question :
S1 : C is younger than D, but older than A and B.
S2 : D is the oldest.
S3 : A is older than B.
Question : Who among A, B, C and D is the youngest?
Which one of the following is correct in respect of the above Statements and the Question?
Answer (d) & explanation
S1 and S3 together are sufficient (d). Step 1: S1 says C is younger than D but older than A and B. So D and C are above A and B. The youngest is A or B. S1 alone is not enough. Step 2: S3 says A is older than B. Combined with S1, B is the youngest. Step 3: S2 (D is oldest) adds nothing new, since S1 already places D above C, A and B. So options (a), (b) and (c) fail.
Tip: in such questions, look for the statement that breaks the final tie. Here S1 narrows it to two people, and S3 decides between them.
Answer as per the official UPSC answer key.
A bottle contains 20 litres of liquid A. 4 litres of liquid A is taken out of it and replaced by same quantity of liquid B. Again 4 litres of the mixture is taken out and replaced by same quantity of liquid B. What is the ratio of quantity of liquid A to that of liquid B in the final mixture?
Answer (c) & explanation
The final ratio of A to B is 16 : 9 (c). Step 1: each round removes 4 of 20 litres, so it keeps 16/20 = 4/5 of liquid A. Step 2: after two rounds: A = 20 × (4/5) × (4/5) = 20 × 16/25 = 12·8 litres. Step 3: B = 20 − 12·8 = 7·2 litres. Ratio 12·8 : 7·2 = 128 : 72 = 16 : 9. Option (a), 4 : 1, is the ratio after only one round (16 : 4). Options (b) and (d) fail.
Tip: for repeated replacement, use: remaining = original × (1 − removed/total)ⁿ. This formula saves step-by-step work.
Answer as per the official UPSC answer key.
Consider the following events in the history of India:
- 1. Rise of Pratiharas under King Bhoja
- 2. Establishment of Pallava power under Mahendravarman — I
- 3. Establishment of Chola power by Parantaka — I
- 4. Pala dynasty founded by Gopala
What is the correct chronological order of the above events, starting from the earliest time ?
Answer (c) & explanation
The order is 2-4-1-3 (c). Mahendravarman I of the Pallavas ruled from about 600 to 630 CE. He built rock-cut temples and wrote the play Mattavilasa Prahasana. Gopala was chosen king in Bengal around 750 CE, founding the Pala dynasty, a rare case of an elected king. Mihira Bhoja brought the Pratiharas to their height from about 836 CE. Parantaka I ruled from 907 CE and spread Chola power, though Vijayalaya founded the line around 850.
These three dynasties, the Palas, Pratiharas and Rashtrakutas, fought the tripartite struggle for Kannauj. Notice the Pala legacy: Dharmapala founded Vikramashila university, and Nalanda flourished under them.
Answer as per the official UPSC answer key.
With reference to Trade-Related Investment Measures (TRIMS), which of the following statements is/are correct ?
- 1. Quantitative restrictions on imports by foreign investors are prohibited.
- 2. They apply to investment measures related to trade in both goods and services.
- 3. They are not concerned with the regulation of foreign investment.
Select the correct answer using the code given below :
Answer (c) & explanation
Statements 1 and 3 are correct (c). The WTO's TRIMs Agreement bans investment rules that distort trade in goods. Statement 1 is right because it prohibits quantitative restrictions on what a foreign investor may import, along with local content requirements and trade-balancing rules. Statement 3 is right because TRIMs does not regulate foreign investment itself; a country may still decide who may invest and how much, as long as the rules do not distort trade. Statement 2 is wrong because TRIMs covers goods only; investment in services falls under GATS.
Notice the other Uruguay Round agreements: TRIPS (intellectual property), GATS (services) and the Agreement on Agriculture. The US once challenged India's solar mission at the WTO over local content rules.
Answer as per the official UPSC answer key.