UPSC Prelims PYQs with explanations
Real questions from official papers, mapped to syllabus topics. Attempt each one; the answer and the reason appear instantly.
Anita's mathematics test had 70 problems carrying equal marks i.e., 10 arithmetic, 30 algebra and 30 geometry. Although she answered 70% of the arithmetic, 40% of the algebra and 60% of the geometry problems correctly, she did not pass the test because she got less than 60% marks. The number of more questions she would have to answer correctly to earn a 60% passing marks is :
Answer (b) & explanation
She needed 5 more correct answers (b). Step 1: count her correct answers. Arithmetic: 70% of 10 = 7. Algebra: 40% of 30 = 12. Geometry: 60% of 30 = 18. Total = 37. Step 2: passing needs 60% of 70 = 42 correct answers. Step 3: she needs 42 − 37 = 5 more. Option (a), 1, is too few. Option (c), 7, and option (d), 9, are too many. Since all questions carry equal marks, you can count questions instead of marks.
Tip: work out each part separately and then add. Do not average the percentages (70, 40 and 60), because each section has a different number of questions.
averaging the three percentages ignores the different section sizes.
Answer as per the official UPSC answer key.
If R and S are different integers both divisible by 5, then which of the following is not necessarily true?
Answer (b) & explanation
"R + S is divisible by 10" is not always true (b). Step 1: R and S are multiples of 5, so write R = 5a and S = 5b. Step 2: R − S = 5(a − b), divisible by 5. R × S = 25ab, divisible by 25. R² + S² = 25(a² + b²), divisible by 5. So options (a), (c) and (d) always hold. Step 3: R + S = 5(a + b). This is divisible by 10 only if a + b is even. Take R = 5 and S = 10. Then R + S = 15, which is not divisible by 10. So (b) is not necessarily true.
Tip: for "not necessarily true", one counter-example is enough. Try the smallest numbers that fit the rules.
Answer as per the official UPSC answer key.
Recently, which one of the following currencies has been proposed to be added to the basket of IMF's SDR?
Answer (d) & explanation
In November 2015 the IMF decided to add the Chinese renminbi (yuan) to the SDR basket from 1 October 2016 (d). The rouble (a), rand (b) and Indian rupee (c) are not in the basket.
The basket now has five currencies: the US dollar, euro, renminbi, yen and pound sterling. The SDR is an international reserve asset created by the IMF in 1969, not a currency itself. Its basket is reviewed every five years. Notice how the renminbi's inclusion marked China's growing role in global finance.
Answer as per the official UPSC answer key.
Which one of the following is the best description of ‘INS Astradharini’, that was in the news recently?
Answer (c) & explanation
INS Astradharini is a torpedo launch and recovery vessel (c). Commissioned in 2015, it was indigenously designed with IIT Kharagpur and the DRDO's Naval Science and Technological Laboratory, and built in Visakhapatnam. It is used to test underwater weapons such as torpedoes. It is not an amphibious ship (a), a nuclear submarine (b) or an aircraft carrier (d).
Its twin-hull (catamaran) design gives stability at sea. For contrast, INS Arihant is India's nuclear-powered ballistic missile submarine, and INS Vikrant is its indigenous aircraft carrier. Notice how such ships show the push for self-reliance in naval technology.
Answer as per the official UPSC answer key.
India is an important member of the ‘International Thermonuclear Experimental Reactor’. If this experiment succeeds, what is the immediate advantage for India?
Answer (d) & explanation
India could build fusion reactors (d). ITER, being built at Cadarache, France, is testing whether a tokamak can produce net energy from fusion, aiming for ten times more energy out than goes into heating its plasma. As one of seven members (EU, India, China, Japan, Korea, Russia, USA), India gets full access to the know-how in return for its share, including the cryostat built by L&T. Thorium (a) belongs to India's separate three-stage fission programme. Satellite navigation (b) is NavIC's field. ITER does nothing for fission reactors (c).
Fusion joins light nuclei, such as deuterium and tritium, and leaves little long-lived waste. Notice India's own tokamaks, Aditya and SST-1, at the Institute for Plasma Research, Gandhinagar.
Answer as per the official UPSC answer key.
A person X was driving in a place where all roads ran either north-south or east-west, forming a grid. Roads are at a distance of 1 km from each other in a parallel. He started at the intersection of two roads, drove 3 km north, 3 km west and 4 km south. Which further route could bring him back to his starting point, if the same route is not repeated ?
Answer (b) & explanation
He should go 3 km east, then 1 km north (b). Step 1: he goes 3 km north and then 4 km south. So he ends 1 km south of the start. He also went 3 km west. Step 2: to get back, he must go 3 km east and 1 km north. Step 3: check the "no repeat" rule. Going east along the road 1 km south of the start is a new road, then 1 km north brings him home. Option (a) takes him further south. Option (c) takes him further west. Option (d) leaves him 3 km south of where he started.
Tip: in direction problems, add up north–south and east–west moves separately. The net gap in each direction tells you the way home.
Answer as per the official UPSC answer key.
Read the passage
By killing transparency and competition, crony capitalism is harmful to free enterprise, opportunity and economic growth. Crony capitalism, where rich and the influential are alleged to have received land and natural resources and various licences in return for payoffs to venal politicians, is now a major issue to be tackled. One of the greatest dangers to growth of developing economies like India is the middle-income trap where crony capitalism creates oligarchies that slow down the growth.
Which among the following is the most logical corollary to the above passage ?
Answer (c) & explanation
The logical corollary is the need for transparency and financial inclusion (c). Step 1: the passage says crony capitalism kills transparency and competition and keeps the poor away from licences and credit. Step 2: so the natural follow-up is more transparency and wider access to finance, which is option (c). Step 3: option (a), more welfare schemes, is never discussed. Option (b) mentions licences for the poor but not the transparency problem. Option (d), manufacturing over services, is not discussed at all.
Tip: a corollary is the solution that follows directly from the problem the passage names. Match the cure to the disease, here secrecy and exclusion.
Answer as per the official UPSC answer key.
A cylindrical overhead tank of radius 2 m and height 7 m is to be filled from an underground tank of size 5·5 m × 4 m × 6 m. How much portion of the underground tank is still filled with water after filling the overhead tank completely?
Answer (a) & explanation
One-third of the underground tank is still full (a). Step 1: the overhead tank is a cylinder. Volume = πr²h = 22/7 × 2 × 2 × 7 = 88 m³. Step 2: the underground tank is a cuboid. Volume = 5.5 × 4 × 6 = 132 m³. Step 3: water left = 132 − 88 = 44 m³. As a fraction: 44 ÷ 132 = 1/3. Option (b), 1/2, and options (c) and (d) do not fit. Here π = 22/7 cancels neatly with the 7 m height.
Tip: when the height is 7 or a multiple of 7, use 22/7 for π. It makes the numbers come out whole.
88/132 = 2/3 is what was taken out. The question asks what is left.
Answer as per the official UPSC answer key.
Consider the following statements :
- 1. The Chief Secretary in a State is appointed by the Governor of that State.
- 2. The Chief Secretary in a State has a fixed tenure.
Which of the statements given above is/are correct?
Answer (d) & explanation
Neither statement is correct (d). The Chief Secretary is not a constitutional post. The officer is chosen by the State government, in practice the Chief Minister's choice, not appointed by the Governor at discretion, so statement 1 is wrong. The post has no fixed tenure; the officer serves at the government's discretion until retirement or transfer, so statement 2 is wrong.
The Chief Secretary is the senior-most civil servant of the State and heads the State secretariat. Notice how the equivalent post at the Centre is the Cabinet Secretary, and how Prakash Singh (2006) gave fixed tenure to police chiefs, not to Chief Secretaries.
Governors appear in so many State appointments that statement 1 sounds automatic. This one is the State government's choice.
Traps like this come back in new clothes. The PYQ Book collects all of them, topic by topic, so none catch you twice. Try the free sample
Answer as per the official UPSC answer key.
Satya Shodhak Samaj organized
Answer (c) & explanation
Satyashodhak Samaj was an anti-caste movement in Maharashtra (c). Jyotiba Phule founded it in Pune in 1873 to free the lower castes and women from Brahminical domination. It held marriages without priests, and Phule and Savitribai Phule ran schools for girls and Dalits. His book Gulamgiri (1873) compared caste with slavery. The other options are wrong: Bihar's tribal movements were Birsa Munda's Ulgulan (a), Gujarat had no such temple-entry campaign (b), and Punjab's peasant movements were unrelated (d). The best-known temple-entry movements were Vaikom (1924–25) and Guruvayur in Kerala.
Phule was given the title "Mahatma" in 1888. Notice how his ideas later shaped the non-Brahmin movement and Dr Ambedkar, who called him one of his three gurus.
Answer as per the official UPSC answer key.
Recently, for the first time in our country, which of the following States has declared a particular butterfly as ‘State Butterfly’?
Answer (d) & explanation
Maharashtra was the first (d). In 2015, Maharashtra declared the Blue Mormon (Papilio polymnestor) its State butterfly. It is a large, velvety black-and-blue swallowtail found mainly in the Western Ghats and Sri Lanka. Arunachal Pradesh (a), Himachal Pradesh (b) and Karnataka (c) were not first. Karnataka later chose the Southern Birdwing, India's largest butterfly, and Kerala chose the Malabar Banded Peacock.
Butterflies are good bio-indicators because they react quickly to habitat and climate change. Notice the trend that followed, as Uttarakhand chose the Common Peacock and Tamil Nadu the Tamil Yeoman. Expect questions on such State symbols, which tie local identity to conservation.
Answer as per the official UPSC answer key.
There is an order of 19000 quantity of a particular product from a customer. The firm produces 1000 quantity of that product per day out of which 5% are unfit for sale. In how many days will the order be completed?
Answer (c) & explanation
The order takes 20 days (c). Step 1: the firm makes 1000 pieces a day, but 5% are unfit. Good pieces per day = 95% of 1000 = 950. Step 2: the customer needs 19,000 good pieces. Days = 19,000 ÷ 950 = 20. Step 3: option (b), 19 days, is the trap: it divides 19,000 by 1000 and forgets the faulty pieces. Option (a), 18, is even less. Option (d), 22, is too many.
Tip: always work with the useful output, after removing waste or defects. A quick check: 950 × 20 = 19,000, which matches the order exactly.
Answer as per the official UPSC answer key.
The total emoluments of two persons are the same, but one gets allowances to the extent of 65% of his basic pay and the other gets allowances to the extent of 80% of his basic pay. The ratio of the basic pay of the former to the basic pay of the latter is :
Answer (d) & explanation
The ratio of their basic pays is 12 : 11 (d). Step 1: the first person's total is basic + 65% of basic = 1.65 × basic. The second person's total is 1.80 × basic. Step 2: the totals are equal, so 1.65 × B1 = 1.80 × B2. Step 3: B1 : B2 = 1.80 : 1.65. Multiply by 100 to get 180 : 165, then divide by 15 to get 12 : 11. The person with the smaller allowance must have the bigger basic pay. Option (a) 16 : 13 and option (b) 5 : 4 are traps from the 80 and 65 figures. Option (c) does not fit.
Tip: if a × X = b × Y, then X : Y = b : a. The ratio flips.
80 : 65 = 16 : 13 forgets that the total is basic + allowance.
Answer as per the official UPSC answer key.
The establishment of 'Payment Banks' is being allowed in India to promote financial inclusion. Which of the following statements is/are correct in this context?
- 1. Mobile telephone companies and supermarket chains that are owned and controlled by residents are eligible to be promoters of Payment Banks.
- 2. Payment Banks can issue both credit cards and debit cards.
- 3. Payment Banks cannot undertake lending activities.
Select the correct answer using the code given below.
Answer (b) & explanation
Statements 1 and 3 are correct (b). Under the RBI's 2014 guidelines, resident-controlled mobile telephone companies, supermarket chains, NBFCs and others can promote Payments Banks (1). They cannot lend (3). Statement 2 is wrong: they can issue debit cards but not credit cards.
Payments Banks take deposits, now up to ₹2 lakh per customer, and offer remittances and bill payments. Examples include India Post Payments Bank and Airtel Payments Bank. They were proposed by the Nachiket Mor committee. Notice how they extend banking to the unbanked without the risks of lending.
a credit card is a loan. A bank that cannot lend cannot issue one.
Answer as per the official UPSC answer key.
‘Net metering’ is sometimes seen in the news in the context of promoting the
Answer (a) & explanation
Net metering promotes the production and use of solar energy by households and consumers (a). A bidirectional meter records power a rooftop solar owner exports to the grid and power drawn from it, and the consumer pays only for the net amount. It has no link to piped natural gas (b), CNG kits in cars (c) or water meters (d).
Gross metering is different: all solar power is sold to the grid at a fixed tariff. Net metering is central to India's rooftop solar programme, including PM Surya Ghar: Muft Bijli Yojana (2024). Notice how it turns consumers into "prosumers", who both produce and consume power.
Answer as per the official UPSC answer key.
Consider the following :
- 1. Calcutta Unitarian Committee
- 2. Tabernacle of New Dispensation
- 3. Indian Reform Association
Keshab Chandra Sen is associated with the establishment of which of the above?
Answer (b) & explanation
Statements 2 and 3 are correct (b). Keshab Chandra Sen set up the Indian Reform Association in 1870 (3) to work for women's education, temperance and cheap literature. This work helped bring the Native Marriage Act, 1872. After a split, he founded the Naba Bidhan (Church of the New Dispensation) in 1880, whose meeting place was called the Tabernacle (2). Statement 1 is wrong because the Calcutta Unitarian Committee (1821–23) was the work of Raja Ram Mohan Roy and William Adam.
Notice the Brahmo splits: Keshab broke from Debendranath Tagore in 1866 to form the Brahmo Samaj of India. After his daughter's underage marriage in 1878, his followers formed the Sadharan Brahmo Samaj.
Answer as per the official UPSC answer key.
The Parliament of India acquires the power to legislate on any item in the State List in the national interest if a resolution to that effect is passed by the
Answer (d) & explanation
The Rajya Sabha decides, by two-thirds of members present and voting (d). Under Article 249, if the Rajya Sabha, as the House representing the States, resolves this way that Parliament should make laws on a State List subject in the national interest, Parliament can do so. The resolution lasts one year and can be renewed one year at a time. The law stops working six months after the resolution ends. The Lok Sabha options (a, b) are wrong, and so is (c), because a simple majority is not enough.
Notice the other routes for central law on State subjects: a national emergency (Art. 250), agreement of two or more States (Art. 252), and international treaties (Art. 253). Rajya Sabha has two similar special powers: Art. 249 and Art. 312, for new All-India Services.
the Lok Sabha options. Only the States' House can open a State subject to Parliament.
Answer as per the official UPSC answer key.
In a class, there are 18 very tall boys. If these constitute three-fourths of the boys and the total number of boys is two-thirds of the total number of students in the class, what is the number of girls in the class?
Answer (b) & explanation
There are 12 girls (b). Step 1: 18 tall boys are three-fourths of the boys. So boys = 18 ÷ 3/4 = 24. Step 2: boys are two-thirds of all students. So students = 24 ÷ 2/3 = 36. Step 3: girls = 36 − 24 = 12. Option (a), 6, is a quarter of the boys, the boys who are not tall. Option (c), 18, is the number of tall boys. Option (d), 21, does not fit.
Tip: "x is a fraction of y" means y = x ÷ fraction. Work backwards one step at a time from the number you know. Check: girls are 12 of 36, which is one-third, the remaining part.
Answer as per the official UPSC answer key.
How many numbers are there between 100 and 300 which either begin with or end with 2?
Answer (a) & explanation
There are 110 such numbers (a). Step 1: between 100 and 300, the numbers that begin with 2 are 200 to 299. That is 100 numbers. Step 2: numbers that end with 2 and begin with 1 are 102, 112, 122 and so on up to 192. That is 10 numbers. The ones ending in 2 that begin with 2, like 202, are already counted. Step 3: total = 100 + 10 = 110. Option (b), 111, counts something twice. Options (c) and (d) do not fit.
Tip: for "either… or" counts, add the two groups and subtract the overlap. Here we simply skipped the overlap. This rule is called inclusion–exclusion.
adding 100 + 20 counts 202, 212, … twice.
Answer as per the official UPSC answer key.
With reference to the International Monetary and Financial Committee (IMFC), consider the following statements :
- 1. IMFC discusses matters of concern affecting the global economy, and advises the International Monetary Fund (IMF) on the direction of its work.
- 2. The World Bank participates as observer in IMFC's meetings.
Which of the statements given above is/are correct?
Answer (c) & explanation
Both are correct (c). The IMFC is a 24-member committee of the IMF Board of Governors, mostly finance ministers and central bank governors. It meets twice a year to discuss matters affecting the global economy and advises the IMF on the direction of its work (1). Several bodies, including the World Bank, attend its meetings as observers (2).
The parallel body for the World Bank is the Development Committee. Both meet during the IMF–World Bank Spring and Annual Meetings. Notice how the Bretton Woods twins coordinate their work through such committees.
Answer as per the official UPSC answer key.