UPSC Prelims PYQs with explanations
Real questions from official papers, mapped to syllabus topics. Attempt each one; the answer and the reason appear instantly.
With reference to ‘Astrosat’, the astronomical observatory launched by India, which of the following statements is/are correct?
- 1. Other than USA and Russia, India is the only country to have launched a similar observatory into space.
- 2. Astrosat is a 2000 kg satellite placed in an orbit at 1650 km above the surface of the Earth.
Select the correct answer using the code given below.
Answer (d) & explanation
Neither statement is correct (d). AstroSat, launched by PSLV-C30 in September 2015, is India's first dedicated multi-wavelength space observatory. It can watch the sky in ultraviolet, visible and X-ray bands at the same time. Statement 1 is wrong because Japan, the European Space Agency and China had also launched space observatories, so India was not the third after the USA and Russia. Statement 2 is wrong because it weighs about 1,513 kg and orbits at about 650 km, not 2,000 kg at 1,650 km.
Its UVIT found extreme-UV light from a distant galaxy (AUDFs01) in 2020. Notice the later Indian science missions: Aditya-L1 (Sun, 2023) and XPoSat (X-ray polarimetry, 2024).
Answer as per the official UPSC answer key.
(Same information as the question above.)
Who is the spouse of R ?
Answer (b) & explanation
R's spouse is T (b). Step 1: T is a man married to someone in the group. Step 2: P and S are unmarried students, so they cannot be T's spouse. Q is the brother of P, so Q is a man, and here the married couple is taken as a man and a woman. Step 3: that leaves R as T's wife. So R's spouse is T. Option (a) P and option (d) S are unmarried. Option (c) Q is a man and P's brother, so he is not the spouse.
Tip: relation clues like "brother" also tell you a person's gender. Note every such hint; it is often the key that settles a marriage question.
Answer as per the official UPSC answer key.
A person climbs a hill in a straight path from point 'O' on the ground in the direction of north-east and reaches a point 'A' after travelling a distance of 5 km. Then, from the point 'A' he moves to point 'B' in the direction of north-west. Let the distance AB be 12 km. Now, how far is the person away from the starting point 'O' ?
Answer (b) & explanation
He is 13 km from the start (b). Step 1: north-east and north-west are at right angles to each other. So O, A and B form a right-angled triangle. Step 2: square the two short sides and add them: 5 × 5 + 12 × 12 = 25 + 144 = 169. Step 3: 13 × 13 = 169, so the distance OB is 13 km. Option (a), 7 km, is 12 − 5. Option (c), 17 km, is 12 + 5. Option (d), 11 km, does not fit.
Tip: learn the common right-triangle sets: 3-4-5, 5-12-13, 8-15-17 and 7-24-25. Seeing 5 and 12 should make you think of 13 at once.
Answer as per the official UPSC answer key.
Which of the following statements is/are correct?
- 1. A Bill pending in the Lok Sabha lapses on its prorogation.
- 2. A Bill pending in the Rajya Sabha, which has not been passed by the Lok Sabha, shall not lapse on dissolution of the Lok Sabha.
Select the correct answer using the code given below.
Answer (b) & explanation
Only statement 2 is correct (b). Prorogation ends a session but does not kill pending Bills (Article 107(3)), so statement 1 is wrong. Dissolution of the Lok Sabha makes Bills pending in the Lok Sabha lapse, but a Bill pending in the Rajya Sabha that the Lok Sabha has not passed survives (Article 107(4)).
Bills passed by the Lok Sabha but pending in the Rajya Sabha do lapse on dissolution. A Bill on which the President has called a joint sitting before dissolution does not lapse. Notice how the Rajya Sabha, a permanent House, keeps legislative work alive across elections.
prorogation and dissolution are different. Only dissolution makes Bills lapse, and only some of them.
Answer as per the official UPSC answer key.
Which of the following best describes/describe the aim of ‘Green India Mission’ of the Government of India?
- 1. Incorporating environmental benefits and costs into the Union and State Budgets thereby implementing the ‘green accounting’
- 2. Launching the second green revolution to enhance agricultural output so as to ensure food security to one and all in the future
- 3. Restoring and enhancing forest cover and responding to climate change by a combination of adaptation and mitigation measures
Select the correct answer using the code given below.
Answer (c) & explanation
Only statement 3 is correct (c). The Green India Mission, one of the eight missions under the National Action Plan on Climate Change (2008), aims to protect, restore and enhance forest cover and respond to climate change through both adaptation and mitigation. Statement 1 is wrong: green accounting in budgets is not its aim. Statement 2 is wrong: a second green revolution in farm output is an agriculture goal, not this mission's.
The mission seeks to improve forest and tree cover on millions of hectares and boost ecosystem services. Notice how it links to India's NDC promise of an extra carbon sink of 2.5–3 billion tonnes of CO₂ equivalent.
Answer as per the official UPSC answer key.
With reference to 'Bitcoins', sometimes seen in the news, which of the following statements is/are correct?
- 1. Bitcoins are tracked by the Central Banks of the countries.
- 2. Anyone with a Bitcoin address can send and receive Bitcoins from anyone else with a Bitcoin address.
- 3. Online payments can be sent without either side knowing the identity of the other.
Select the correct answer using the code given below.
Answer (b) & explanation
Statements 2 and 3 are correct (b). Bitcoin (2009, created by "Satoshi Nakamoto") is a decentralised cryptocurrency. Its transactions are recorded on a public blockchain kept up by a network of users, so statement 1 is wrong: no central bank tracks or issues it. Anyone with a Bitcoin address can send coins to and receive them from any other address, peer to peer (2). Users are known only by their addresses, so payments can be made without either side knowing the other's real identity (3). This is called being pseudonymous.
In India, crypto gains are taxed at 30% with 1% TDS, and exchanges must register with the FIU-IND. Notice the contrast with the RBI's e-rupee (CBDC), which is a central-bank-issued, legal-tender digital currency.
central banks issue and manage fiat money. Bitcoin's whole design avoids any central authority.
Answer as per the official UPSC answer key.
A recent movie titled The Man Who Knew Infinity is based on the biography of
Answer (a) & explanation
The film is about S. Ramanujan (a). The Man Who Knew Infinity (2015), with Dev Patel, tells the story of self-taught mathematician Srinivasa Ramanujan (1887–1920) and his work with G. H. Hardy at Cambridge. It is based on Robert Kanigel's 1991 biography. Ramanujan became a Fellow of the Royal Society in 1918 and is famous for work on partitions, infinite series and the "taxicab number" 1729. S. Chandrasekhar (b) is known for the Chandrasekhar limit. S. N. Bose (c) gave his name to bosons. C. V. Raman (d) discovered the Raman effect.
22 December, Ramanujan's birthday, is National Mathematics Day. Notice that 28 February, the day Raman announced his effect in 1928, is National Science Day.
Answer as per the official UPSC answer key.
30 g of sugar was mixed in 180 ml water in a vessel A, 40 g of sugar was mixed in 280 ml of water in vessel B and 20 g of sugar was mixed in 100 ml of water in vessel C. The solution in vessel B is :
Answer (d) & explanation
Vessel B is less sweet than vessel C (d). Step 1: sweetness = sugar ÷ water. A = 30/180 = 1/6. B = 40/280 = 1/7. C = 20/100 = 1/5. Step 2: compare the fractions. 1/5 is bigger than 1/6, which is bigger than 1/7. So C is sweetest and B is least sweet. Step 3: so B is less sweet than C, option (d). Option (a) says the opposite. Option (b) is wrong because B is less sweet than A too. Option (c) is wrong because B and C are not equal.
Tip: to compare mixtures, turn each into "per unit" form and simplify. With the same numerator 1, a smaller denominator means a stronger mixture.
Answer as per the official UPSC answer key.
Ram and Shyam work on a job together for four days and complete 60% of it. Ram takes leave then and Shyam works for eight more days to complete the job. How long would Ram take to complete the entire job alone?
Answer (c) & explanation
Ram alone would take 10 days (c). Step 1: together, 60% in 4 days means 15% per day together. Step 2: Shyam alone finishes the last 40% in 8 days, so Shyam does 5% per day. Step 3: Ram's rate = 15% − 5% = 10% per day. The whole job takes Ram 100 ÷ 10 = 10 days. Option (a), 6 days, and option (b), 8 days, are too fast. Option (d), 11 days, is too slow.
Tip: turn work into "percent per day" or "units per day". Rates add when people work together, so you can subtract to find one person's rate. Check: Ram and Shyam do 10% + 5% = 15% a day, which matches.
Answer as per the official UPSC answer key.
Which of the following is/are included in the capital budget of the Government of India?
- 1. Expenditure on acquisition of assets like roads, buildings, machinery, etc.
- 2. Loans received from foreign governments
- 3. Loans and advances granted to the States and Union Territories
Select the correct answer using the code given below.
Answer (d) & explanation
All three are included (d). The capital budget has capital receipts and capital expenditure. Loans received from foreign governments (2) are capital receipts because they create a liability. Acquiring assets such as roads and buildings (1) and loans to States and UTs (3) are capital expenditure because they create an asset or a claim.
The revenue budget, by contrast, covers taxes, interest and day-to-day spending that create no asset or liability. The government has pushed capital spending to over ₹11 lakh crore to boost growth. Notice how capital spending has a bigger multiplier effect than revenue spending.
statement 2 is a receipt, not spending. The capital budget covers both sides.
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Answer as per the official UPSC answer key.
What is/are unique about ‘Kharai camel’, a breed found in India?
- 1. It is capable of swimming up to three kilometres in seawater.
- 2. It survives by grazing on mangroves.
- 3. It lives in the wild and cannot be domesticated.
Select the correct answer using the code given below.
Answer (a) & explanation
Statements 1 and 2 are correct (a). The Kharai camel ("kharai" means saline) of Kachchh, Gujarat, can swim up to about 3 km in seawater (1) to reach the islands of the Gulf of Kachchh, where it feeds on mangroves (2). Statement 3 is wrong: it is a domesticated breed, reared by Rabari and Fakirani Jat herders.
It was recognised as a distinct breed in 2015. Mangrove loss, salt pans and industry along the coast threaten its grazing grounds. Notice how this links pastoral communities, coastal ecology and breed conservation; the Marine National Park in the Gulf of Kachchh lies in the same region.
Answer as per the official UPSC answer key.
The term ‘Regional Comprehensive Economic Partnership’ often appears in the news in the context of the affairs of a group of countries known as
Answer (b) & explanation
RCEP is linked with ASEAN (b). The Regional Comprehensive Economic Partnership was negotiated by the 10 ASEAN countries and their six FTA partners: China, Japan, South Korea, Australia, New Zealand and India. India walked out in November 2019. It feared a flood of cheap Chinese goods, harm to dairy and farm sectors, and weak safeguards. The other 15 signed in November 2020, and the deal came into force in 2022. It is not a G20 (a), SCO (c) or SAARC (d) project.
It is the world's largest trade bloc, covering about 30% of global GDP. Notice India's other path: it reviews its ASEAN FTA (AITIGA) and signs bilateral deals such as with the UAE, Australia, EFTA and the UK.
Answer as per the official UPSC answer key.
A ate grapes and pineapple; B ate grapes and oranges; C ate oranges, pineapple and apple; D ate grapes, apple and pineapple. After taking fruits, B and C fell sick. In the light of the above facts, it can be said that the cause of sickness was :
Answer (d) & explanation
The cause of sickness was oranges (d). Step 1: B and C fell sick. A and D stayed well. Look for a fruit that both sick people ate and neither healthy person ate. Step 2: B ate grapes and oranges. C ate oranges, pineapple and apple. The fruit common to B and C is oranges. Step 3: check the healthy pair. A ate grapes and pineapple, and D ate grapes, apple and pineapple. Neither ate oranges. Apple (a) and pineapple (b) were eaten by A or D, who stayed well. Grapes (c) were eaten by both A and D.
Tip: in "find the cause" puzzles, the cause appears in every bad case and in none of the good ones. Remove anything a healthy person also had.
Answer as per the official UPSC answer key.
A piece of tin is in the form of a rectangle having length 12 cm and width 8 cm. This is used to construct a closed cube. The side of the cube is :
Answer (c) & explanation
The side of the cube is 4 cm (c). Step 1: the tin sheet's area is 12 × 8 = 96 cm². Step 2: a closed cube has 6 equal square faces. So each face = 96 ÷ 6 = 16 cm². Step 3: 16 = 4 × 4, so each side is 4 cm. Option (a), 2 cm, gives only 24 cm² of surface. Option (b), 3 cm, gives 54 cm². Option (d), 6 cm, would need 216 cm², more than the sheet.
Tip: the surface area of a cube is 6 × side × side. When a sheet is "used to make" a solid, set the sheet's area equal to the solid's surface area, not its volume.
Answer as per the official UPSC answer key.
Read the passage
Historically, the biggest challenge to world agriculture has been to achieve a balance between demand for and supply of food. At the level of individual countries, the demand-supply balance can be a critical policy issue for a closed economy, especially if it is a populous economy and its domestic agriculture is not growing sufficiently enough to ensure food supplies, on an enduring basis; it is not so much and not always, of a constraint for an open, and growing economy, which has adequate exchange surpluses to buy food abroad. For the world as a whole, supply-demand balance is always an inescapable prerequisite for warding off hunger and starvation. However, global availability of adequate supply does not necessarily mean that food would automatically move from countries of surplus to countries of deficit if the latter lack in purchasing power. The uneven distribution of hunger, starvation, under- or malnourishment, etc., at the world-level, thus owes itself to the presence of empty-pocket hungry mouths, overwhelmingly confined to the underdeveloped economies. Inasmuch as ‘a two-square meal’ is of elemental significance to basic human existence, the issue of worldwide supply of food has been gaining significance, in recent times; both because the quantum and the composition of demand has been undergoing big changes, and because, in recent years, the capabilities of individual countries to generate uninterrupted chain of food supplies have come under strain. Food production, marketing and prices, especially price-affordability by the poor in the developing world, have become global issues that need global thinking and global solutions.
The issue of worldwide supply of food has gained importance mainly because of :
- 1. overgrowth of the population worldwide
- 2. sharp decline in the area of food production
- 3. limitation in the capabilities for sustained supply of food
Select the correct answer using the code given below :
Answer (b) & explanation
Only statement 3 is the reason (b). Step 1: the passage says world food supply matters because "the capabilities of individual countries to generate uninterrupted chain of food supplies have come under strain". That is statement 3, the limit on steady supply. Step 2: population overgrowth (1) is not stated as the reason. Step 3: a sharp fall in food-growing area (2) is also not stated. So options (a), (c) and (d) fail.
Tip: avoid choosing an option just because it is true in real life. Population growth does raise food demand, but the question asks what the passage gives as the reason. Stay inside the passage.
Answer as per the official UPSC answer key.
Which of the following are the key features of ‘National Ganga River Basin Authority (NGRBA)’?
- 1. River basin is the unit of planning and management.
- 2. It spearheads the river conservation efforts at the national level.
- 3. One of the Chief Ministers of the States through which the Ganga flows becomes the Chairman of NGRBA on rotation basis.
Select the correct answer using the code given below.
Answer (a) & explanation
Statements 1 and 2 are correct (a). The NGRBA, set up in 2009 under the Environment (Protection) Act, treated the river basin as the unit of planning and management (1) and led river conservation at the national level (2). Statement 3 is wrong: the Prime Minister chaired it, not a rotating Chief Minister.
In 2016 it was replaced by the National Ganga Council, also headed by the PM, with the National Mission for Clean Ganga under it, which runs Namami Gange. Notice how basin-level planning recognises that a river's health depends on its whole catchment.
Answer as per the official UPSC answer key.
With reference to 'Financial Stability and Development Council', consider the following statements :
- 1. It is an organ of NITI Aayog.
- 2. It is headed by the Union Finance Minister.
- 3. It monitors macroprudential supervision of the economy.
Which of the statements given above is/are correct?
Answer (c) & explanation
Statements 2 and 3 are correct (c). The Financial Stability and Development Council (FSDC) was set up in 2010 by executive order after the global financial crisis. It is chaired by the Union Finance Minister (2). Its members include the heads of the RBI, SEBI, IRDAI, PFRDA and IBBI. It oversees macroprudential supervision of the economy and also looks after inter-regulator coordination and financial literacy and inclusion (3). Statement 1 is wrong because it sits under the Ministry of Finance, not NITI Aayog.
Note that it is not a statutory body. Its sub-committee is chaired by the RBI Governor. Notice the difference between the two kinds of supervision: macroprudential looks at risk to the whole system, while microprudential looks at one bank at a time.
"organ of NITI Aayog" also appeared for NIIF in 2017 Q55. Both are Finance Ministry bodies.
Answer as per the official UPSC answer key.
With reference to the economic history of medieval India, the term ‘Araghatta’ refers to
Answer (c) & explanation
Araghatta was a water-wheel for irrigation (c). It carried a chain of pots and was turned by bullocks, lifting water from wells to the fields. Early medieval texts and inscriptions mention it, and it later developed into the gear-driven Persian wheel (saqiya/rahat), which spread widely under the Delhi Sultanate. It does not mean bonded labour (a). Land grants to military officers (b) were iqtas under the Sultanate and jagirs under the Mughals. Wasteland brought under the plough (d) does not match the word either.
Notice the story of farm technology: wells, tanks (eri) and the araghatta made it possible to grow two crops a year. Babur's memoirs describe the water-wheels he saw in north India.
Answer as per the official UPSC answer key.
(Same information as the question above.)
Who is the lawyer ?
Answer (b) & explanation
Q is the lawyer (b). Step 1: the jobs are doctor, lawyer and artist. P and S are students, so the jobs belong to Q, R and T. Step 2: Q is neither doctor nor artist. The only job left for Q is lawyer. Step 3: check the rest. R is not the doctor, so R is the artist and T is the doctor. Option (a) P and option (d) S are students. Option (c) R is the artist.
Tip: a clue that rules out two of three choices fixes the third straight away. Look for such clues first. Here the clue about Q settles the lawyer before you need anything else.
Answer as per the official UPSC answer key.
An agricultural field is in the form of a rectangle having length X1 meters and breadth X2 meters (X1 and X2 are variable). If X1 + X2 = 40 meters, then the area of the agricultural field will not exceed which one of the following values?
Answer (a) & explanation
The area cannot exceed 400 sq m (a). Step 1: length + breadth = 40 m. Step 2: for a fixed sum, the product is largest when the two parts are equal. So the best is 20 × 20. Step 3: maximum area = 400 sq m. Try others: 30 × 10 = 300 and 35 × 5 = 175, both smaller. So options (b) 300, (c) 200 and (d) 80 are possible areas, but the question asks for the value it will not exceed.
Tip: among rectangles with the same perimeter, the square has the largest area. This idea comes up often in CSAT.
Answer as per the official UPSC answer key.