UPSC Prelims PYQs with explanations
Real questions from official papers, mapped to syllabus topics. Attempt each one; the answer and the reason appear instantly.
Using 2, 2, 3, 3, 3 as digits, how many distinct numbers greater than 30000 can be formed ?
Answer (b) & explanation
Six numbers can be formed (b). Step 1: all numbers use all five digits, so they are 5-digit numbers. To be above 30000, the first digit must be 3. Step 2: the remaining digits are 2, 2, 3, 3. The number of ways to arrange them is 4! ÷ (2! × 2!) = 6. Step 3: they are 2233, 2323, 2332, 3223, 3232 and 3322. Options (a), (c) and (d) miscount by ignoring or double-counting the repeated digits.
Tip: when digits repeat, divide by the factorial of each repeat count. Without this, you would count the same number many times.
Answer as per the official UPSC answer key.
With reference to furnace oil, consider the following statements :
- 1. It is a product of oil refineries.
- 2. Some industries use it to generate power.
- 3. Its use causes sulphur emissions into environment.
Which of the statements given above are correct?
Answer (d) & explanation
All three statements are correct (d). Statement 1 is right: furnace oil is a heavy, dark fuel left after the lighter fractions, such as petrol and diesel, are taken out at an oil refinery. Statement 2 is right: factories burn it in boilers, furnaces and generators to make heat and power. Statement 3 is right: it is high in sulphur, so burning it releases sulphur dioxide.
Notice that the Supreme Court banned furnace oil and pet coke in Delhi-NCR in 2017 to fight air pollution. Ships face similar limits: the IMO 2020 rule cut sulphur in marine fuel to 0.5%. India moved to BS-VI fuel in 2020, with sulphur limited to 10 ppm.
Answer as per the official UPSC answer key.
With reference to 'palm oil', consider the following statements :
- 1. The palm oil tree is native to Southeast Asia.
- 2. The palm oil is a raw material for some industries producing lipstick and perfumes.
- 3. The palm oil can be used to produce biodiesel.
Which of the statements given above are correct?
Answer (b) & explanation
Statements 2 and 3 are correct (b). Statement 1 is wrong: the oil palm is native to West Africa, though Indonesia and Malaysia now grow most of the world's palm oil. Statement 2 is right: palm oil goes into lipsticks, perfumes, soaps, shampoos and processed food, because it is cheap and stable. Statement 3 is right: palm oil is a feedstock for biodiesel, especially in Indonesia and Malaysia.
Notice India's angle: India is the world's largest importer of palm oil and of edible oils. The National Mission on Edible Oils–Oil Palm (2021) aims to expand oil palm in the North-East and the Andaman and Nicobar Islands. Critics warn of deforestation and harm to biodiversity, as seen in South-east Asia.
today's production map points to Southeast Asia. The plant's original home is Africa.
Answer as per the official UPSC answer key.
At the national level, which ministry is the nodal agency to ensure effective implementation of the Scheduled Tribes and Other Traditional Forest Dwellers (Recognition of Forest Rights) Act, 2006?
Answer (d) & explanation
The Ministry of Tribal Affairs is the nodal agency (d). The Forest Rights Act, 2006 recognises the rights of forest-dwelling Scheduled Tribes and other traditional forest dwellers over land they cultivate and forest resources they use. Because it is a law for tribal and forest communities, the Ministry of Tribal Affairs is its nodal ministry. Option (a) is a trap: the Environment Ministry handles forest conservation laws, such as the Forest (Conservation) Act. Options (b) and (c) are wrong: Panchayati Raj and Rural Development have no nodal role, though the gram sabha is central to the Act.
Notice the three kinds of rights: individual, community and community forest resource rights. Mendha Lekha in Maharashtra got the first community forest rights.
(a): the word "Forest" in the Act's name pulls you to MoEFCC.
Answer as per the official UPSC answer key.
Read the passage
Computers increasingly deal not just with abstract data like credit card details and databases, but also with the real world of physical objects and vulnerable human bodies. A modern car is a computer on wheels; an aeroplane is a computer on wings. The arrival of the “Internet of Things” will see computers baked into everything from road signs and MRI scanners to prosthetics and insulin pumps. There is little evidence that these gadgets will be any more trustworthy than their desktop counterparts. Hackers have already proved that they can take remote control of internet connected cars and pacemakers.
Which one of the following statements best reflects the most critical inference that can be made from the passage given above ?
Answer (a) & explanation
The critical inference is that computers are not completely safe (a). Step 1: the passage says hackers have taken control of connected cars and pacemakers. If such devices can be hacked, computers are not fully safe. That is (a). Step 2: option (b) blames companies for not taking security seriously; the passage does not say this. Option (c) asks for new laws; this also goes beyond the passage. Step 3: option (d), technology will affect our lives, is too vague to be the critical inference.
Tip: the safest inference stays closest to the facts given. Blame and remedies usually go beyond a passage that only reports events.
Answer as per the official UPSC answer key.
Consider the following Table :
| Player | Runs scored in the First Innings | Balls faced in the First Innings | Runs scored in the Second Innings | Balls faced in the Second Innings |
|---|---|---|---|---|
| A | 61 | 99 | 14 | 76 |
| B | 05 | 12 | 50 | 85 |
| C | 15 | 75 | 20 | 50 |
| D | 13 | 55 | 12 | 50 |
Who is the fastest run scorer in the Test Match ?
Answer (b) & explanation
B is the fastest scorer (b). Step 1: "fastest" means the most runs per ball over the whole match, not in one innings. So add both innings for each player. Step 2: A scored 75 in 175 balls, about 0.43 runs per ball. B scored 55 in 97 balls, about 0.57. Step 3: C scored 35 in 125 balls (0.28) and D scored 25 in 105 balls (0.24). B has the highest rate, so (b). Option (a), A, has the most runs, but took many more balls.
Tip: speed means a rate, not a total. Divide runs by balls; in cricket, strike rate = runs per 100 balls.
A's first innings looks the most striking, but you have to add both innings before you compare.
Answer as per the official UPSC answer key.
X said to Y, "At the time of your birth I was twice as old as you are at present." If the present age of X is 42 years, then consider the following statements :
- 1. 8 years ago, the age of X was five times the age of Y.
- 2. After 14 years, the age of X would be two times the age of Y.
Which of the above statements is/are correct ?
Answer (b) & explanation
Only statement 2 is correct (b). Step 1: when Y was born, X's age equalled the age gap. That gap is twice Y's present age. So X − Y = 2Y, which means X = 3Y. With X = 42, Y = 14. Step 2: statement 1: 8 years ago, X was 34 and Y was 6. 34 is not 5 × 6 = 30, so it is false. Step 3: statement 2: after 14 years, X will be 56 and Y 28. 56 = 2 × 28, so it is true. Options (a), (c) and (d) fail.
Tip: the age gap between two people never changes. "At your birth I was ..." gives you that gap directly.
Answer as per the official UPSC answer key.
The ‘Common Carbon Metric’, supported by UNEP, has been developed for
Answer (a) & explanation
It assesses the carbon footprint of building operations (a). The Common Carbon Metric was developed by UNEP's Sustainable Buildings and Climate Initiative (UNEP-SBCI). It gives one standard way to measure the energy use and greenhouse gas emissions of buildings in operation, so that buildings anywhere in the world can be compared and reported on the same basis. Option (b) is wrong: it is not for farm carbon trading. Option (c) is wrong: national footprints are reported through UNFCCC inventories. Option (d) is wrong: it does not measure global fossil fuel use.
Notice that buildings account for nearly 40% of global energy-related emissions. India's tools include the Energy Conservation Building Code (ECBC) and the GRIHA green rating system.
Answer as per the official UPSC answer key.
Consider the following statements :
- 1. Moringa (drumstick tree) is a leguminous evergreen tree.
- 2. Tamarind tree is endemic to South Asia.
- 3. In India, most of the tamarind is collected as minor forest produce.
- 4. India exports tamarind and seeds of moringa.
- 5. Seeds of moringa and tamarind can be used in the production of biofuels.
Which of the statements given above are correct?
Answer (b) & explanation
Statements 3, 4 and 5 are correct (b). Statement 1 is wrong: moringa (drumstick) belongs to its own family, Moringaceae, not the legumes, and it is deciduous, shedding its leaves in the dry season. Statement 2 is wrong: tamarind came from tropical Africa, so it is not endemic to South Asia. Statement 3 is right: most Indian tamarind is gathered from forests and village trees as minor forest produce. Statement 4 is right: India exports both tamarind and moringa seeds. Statement 5 is right: the seed oils of both can be used to make biofuel.
Notice that India is the world's largest producer of moringa. Tamarind is among the items under MSP for minor forest produce, run through TRIFED.
tamarind is so Indian in the kitchen that "endemic" feels right.
Answer as per the official UPSC answer key.
Consider the following statements in respect of the Laureus World Sports Award which was instituted in the year 2000 :
- 1. American golfer Tiger Woods was the first winner of this award.
- 2. The award was received mostly by ‘Formula One’ players so far.
- 3. Roger Federer received this award a maximum number of times compared to others.
Which of the above statements are correct?
Answer (c) & explanation
Statements 1 and 3 are correct (c). Statement 1 is right: Tiger Woods won the first Laureus World Sportsman of the Year award in 2000. Statement 3 was right when asked: Roger Federer had won it the most times, five; Novak Djokovic has since equalled him with his fifth in 2024. Statement 2 is wrong: winners have come from tennis, athletics, golf, football and swimming, as well as Formula One (Michael Schumacher, Lewis Hamilton), so it is not mostly F1.
Notice India's Laureus moment: Sachin Tendulkar won the Laureus Sporting Moment award (2000–2020) in 2020, for being carried on teammates' shoulders after the 2011 World Cup win. The awards were founded by Daimler and Richemont.
Answer as per the official UPSC answer key.
Read the passage
A central message of modern development economics is the importance of income growth, by which is meant growth in Gross Domestic Product (GDP). In theory, rising GDP creates employment and investment opportunities. As incomes grow in a country where the level of GDP was once low, households, communities, and governments are increasingly able to set aside some funds for the production of things that make for a good life. Today GDP has assumed such a significant place in the development lexicon, that if someone mentions “economic growth”, we know they mean growth in GDP.
With reference to the above passage, the following assumptions have been made :
- 1. Rising GDP is essential for a country to be a developed country.
- 2. Rising GDP guarantees a reasonable distribution of income to all households.
Which of the above assumptions is/are valid ?
Answer (d) & explanation
Neither assumption is valid (d). Step 1: the passage reports what development economics says "in theory" about GDP. It does not call GDP growth essential for becoming developed. So assumption 1 fails. Step 2: assumption 2 says rising GDP guarantees fair income for all households. The passage says nothing about distribution. So 2 fails. Step 3: options (a), (b) and (c) fail.
Tip: reporting a theory is not endorsing it. Also, "guarantees" is a very strong word. GDP measures total output; it can rise even while inequality grows, which is why measures like the Human Development Index exist.
Answer as per the official UPSC answer key.
In a code language 'MATHEMATICS' is written as 'LBSIDNZUHDR'. How is 'CHEMISTRY' written in that code language ?
Answer (b) & explanation
CHEMISTRY is written BIDNHTSSX (b). Step 1: compare MATHEMATICS with LBSIDNZUHDR letter by letter. M → L (−1), A → B (+1), T → S (−1), H → I (+1). The moves alternate −1, +1. Step 2: apply this to CHEMISTRY: C−1 = B, H+1 = I, E−1 = D, M+1 = N, I−1 = H, S+1 = T, T−1 = S, R+1 = S, Y−1 = X. Step 3: the code is BIDNHTSSX. Option (c) has L and T, getting M wrong. Options (a) and (d) start with the wrong move.
Tip: in coding questions, check the first four letters to find the pattern. Then look at only the letters where the options differ.
Answer as per the official UPSC answer key.
Consider the following statements :
The effect of devaluation of a currency is that it necessarily
- 1. improves the competitiveness of the domestic exports in the foreign markets
- 2. increases the foreign value of domestic currency
- 3. improves the trade balance
Which of the above statements is/are correct?
Answer (a) & explanation
Only statement 1 is correct (a). Devaluation is a deliberate cut in the value of the currency against foreign currencies, under a fixed or managed rate. Statement 1 is right: Indian goods become cheaper abroad, so exports become more competitive. Statement 2 is wrong: devaluation reduces, not increases, the currency's foreign value. Statement 3 is wrong because of the word "necessarily": imports such as oil become dearer, and if demand does not respond quickly, the trade deficit may first widen. This is the J-curve effect.
Notice India's big devaluations in 1966 and 1991. Note the difference: devaluation is a policy step under a fixed rate; depreciation is a market fall under a floating rate.
the word "necessarily". It turns statement 3 from possible into wrong.
Answer as per the official UPSC answer key.
With reference to the history of ancient India, which of the following statements is/are correct?
- 1. Mitakshara was the civil law for upper castes and Dayabhaga was the civil law for lower castes.
- 2. In the Mitakshara system, the sons can claim right to the property during the lifetime of the father, whereas in the Dayabhaga system, it is only after the death of the father that the sons can claim right to the property.
- 3. The Mitakshara system deals with the matters related to the property held by male members only of a family, whereas the Dayabhaga system deals with the matters related to the property held by both male and female members of a family.
Select the correct answer using the code given below.
Answer (b) & explanation
Only statement 2 is correct (b). Statement 1 is wrong: the two schools of Hindu law differ by region, not caste. Dayabhaga, by Jimutavahana, applied in Bengal and Assam; Mitakshara, by Vijnaneshwara, applied in the rest of India. Statement 2 is right: under Mitakshara, a son gets a share in ancestral property by birth, so he can claim it in the father's lifetime; under Dayabhaga, sons inherit only on the father's death. Statement 3 is wrong: both schools also cover women's property, called stridhana.
Notice that Vijnaneshwara wrote the Mitakshara as a commentary on the Yajnavalkya Smriti at the court of the Chalukya king Vikramaditya VI. The Hindu Succession (Amendment) Act, 2005 gave daughters equal coparcenary rights.
Answer as per the official UPSC answer key.
Bisphenol A (BPA), a cause of concern, is a structural/key component in the manufacture of which of the following kinds of plastics?
Answer (b) & explanation
BPA is a key component of polycarbonate (b). Bisphenol A is the building block of hard, clear polycarbonate plastic, used in water bottles and food containers, and of epoxy resins that line food cans. It can leach into food and drinks, especially when heated, and acts like the hormone oestrogen, making it an endocrine disruptor. Low-density polyethylene (a) is used in bags. PET (c) is used in most soft-drink bottles. PVC (d) is used in pipes. None of them is built from BPA.
Notice that India, through the BIS, banned BPA in baby feeding bottles in 2015. Phthalates are another group of plastic chemicals that disrupt hormones.
Answer as per the official UPSC answer key.
Read the passage
A study conducted on the impacts of climate change over the Cauvery basin of Tamil Nadu using regional climate models showed an increasing trend for maximum and minimum temperatures, and a decrease in the number of rainy days. These climatic shifts will have an impact on the hydrological cycles in the region, lead to more run-off and less recharge, and affect the groundwater tables. Further, there has been an increase in the frequency of droughts in the State. This has driven farmers to increase dependency on groundwater resources to secure their crops.
Which one of the following statements best reflects the crux of the passage given above ?
Answer (c) & explanation
The crux is that climate change makes water more critical while also threatening it (c). Step 1: the passage says climate change cuts groundwater recharge. At the same time, more droughts raise farmers' dependence on groundwater. So water becomes more important and more at risk together. That is (c). Step 2: options (a) and (b) bring in remedies: regional climate models and dry-land cropping. The passage's main point is the problem, not these fixes. Step 3: option (d), farmers adopting risky livelihoods, is a side detail, not the crux.
Tip: the crux captures the passage's central tension. When a passage shows a "double squeeze", choose the option that names both sides.
Answer as per the official UPSC answer key.
In a group of 120 persons, 80 are Indians and rest are foreigners. Further, 70 persons in the group can speak English. The number of Indians who can speak English is
Answer (d) & explanation
The number of Indians who speak English is 30 or more (d). Step 1: there are 120 people: 80 Indians and 40 foreigners. Step 2: 70 people speak English. Even if all 40 foreigners speak English, at least 70 − 40 = 30 speakers must be Indian. Step 3: if fewer foreigners speak English, more Indians must. It can go up to all 70. So the answer is "30 or more". Option (a), exactly 20, is impossible, and option (b), exactly 30, is only the least case. Option (c), 30 or less, gets the direction wrong.
Tip: for "at least" questions, give the other group the most it can take. What is left is the minimum for your group.
the question asks for what must be true. Find the smallest overlap, not an exact number.
Answer as per the official UPSC answer key.
Consider the following statements :
- 1. The sum of 5 consecutive integers can be 100.
- 2. The product of three consecutive natural numbers can be equal to their sum.
Which of the above statements is/are correct ?
Answer (c) & explanation
Both statements are correct (c). Step 1: the sum of 5 consecutive integers is 5 × the middle one. 100 = 5 × 20, so 18 + 19 + 20 + 21 + 22 = 100. Statement 1 is true. Step 2: for statement 2, try small natural numbers: 1 × 2 × 3 = 6, and 1 + 2 + 3 = 6. They are equal, so statement 2 is true. Step 3: so options (a), (b) and (d) fail.
Tip: for consecutive numbers, the sum = count × middle value (with an odd count). For "can be" statements, one example is enough to prove it true.
Answer as per the official UPSC answer key.
What is blue carbon?
Answer (a) & explanation
Blue carbon is carbon captured by oceans and coastal ecosystems (a). Blue carbon is the carbon stored by ocean and coastal ecosystems, mainly mangroves, salt marshes and seagrass meadows. Area for area, they lock away carbon much faster than land forests and keep it in their waterlogged soils for centuries. Option (b) describes green carbon, held in land forests and soils. Option (c) describes fossil carbon in petroleum and natural gas, sometimes called brown or black carbon. Option (d) describes carbon already in the atmosphere, mostly as CO₂.
Notice the MISHTI scheme (2023) for planting mangroves along India's coasts. Sundarbans is the world's largest mangrove forest. Losing these habitats releases their stored carbon.
Answer as per the official UPSC answer key.
With reference to the Indus river system, of the following four rivers, three of them pour into one of them which joins the Indus direct. Among the following, which one is such river that joins the Indus direct?
Answer (d) & explanation
The Sutlej joins the Indus directly (d). Among the Punjab rivers, the Jhelum joins the Chenab first. The Ravi then joins the Chenab. The Chenab then joins the Sutlej, which has already received the Beas. The combined stream, called the Panjnad ("five rivers"), meets the Indus near Mithankot in Pakistan. So the Sutlej carries the water of all the others into the Indus. Options (a), (b) and (c) are wrong because the Chenab, Jhelum and Ravi all reach the Indus only through the Sutlej.
Notice the Indus Waters Treaty (1960): India controls the eastern rivers (Ravi, Beas, Sutlej); Pakistan gets the western rivers (Indus, Jhelum, Chenab). India put the treaty in abeyance in April 2025; a Hague court called this invalid in August 2026, but India rejects that ruling.
Many answer the Chenab because it collects the Jhelum and the Ravi. But the Chenab itself flows into the Sutlej before reaching the Indus.
Answer as per the official UPSC answer key.