UPSC Prelims PYQs with explanations
Real questions from official papers, mapped to syllabus topics. Attempt each one; the answer and the reason appear instantly.
Consider the following statements :
Statement-I :
India accounts for 3.2% of global export of goods.
Statement-II :
Many local companies and some foreign companies operating in India have taken advantage of India's 'Production-linked Incentive' scheme.
Which one of the following is correct in respect of the above statements?
Answer (d) & explanation
Statement I is wrong but Statement II is correct (d). Statement I is wrong: India's share of world merchandise exports is only about 1.8%, not 3.2%. Its share of services exports is much higher, over 4%, led by IT and business services. Statement II is right: the Production-Linked Incentive scheme (2020) covers 14 sectors, such as mobile phones, pharmaceuticals, solar modules and automobiles, and has drawn both Indian firms and foreign ones such as Apple's suppliers Foxconn and Pegatron.
Notice the success story: India is now a major smartphone exporter, and phones have become one of its top export items. PLI pays firms a share of their extra sales, to boost manufacturing and cut imports.
the 3.2% figure is close to India's share of world GDP or services trade. For goods it is far lower.
Answer as per the official UPSC answer key.
For any choices of values of X, Y and Z, the 6-digit number of the form XYZXYZ is divisible by :
Answer (d) & explanation
XYZXYZ is always divisible by 7, 11 and 13 (d). Step 1: write it out: XYZXYZ = XYZ × 1000 + XYZ = XYZ × 1001. Step 2: 1001 = 7 × 11 × 13. Step 3: so every such number is divisible by all three. Options (a), (b) and (c) each leave one out. For example, 123123 = 123 × 7 × 11 × 13.
Tip: 1001 = 7 × 11 × 13 is worth remembering. Any 3-digit block written twice is a multiple of 1001.
Answer as per the official UPSC answer key.
If today is Sunday, then which day is it exactly on 1010 th day ?
Answer (a) & explanation
The 10¹⁰th day is a Wednesday (a). Step 1: today (Sunday) is day 1. So the 10¹⁰th day is 10¹⁰ − 1 days later. Step 2: 10 leaves remainder 3 when divided by 7. So 10¹⁰ leaves the same remainder as 3¹⁰. Since 3⁶ leaves 1, 3¹⁰ leaves the same as 3⁴ = 81, which is 4. Step 3: so 10¹⁰ − 1 leaves 3. Sunday + 3 days = Wednesday. Option (b), Thursday, forgets that today is day 1.
Tip: "the nth day" counting today as day 1 means n − 1 days ahead. This off-by-one trap is common.
today is day 1, not day 0. Counting it as day 0 gives Thursday, which is an option.
UPSC repeats traps like this year after year. The PYQ Book gathers every trap in one place, so you see them coming. Try the free sample
Answer as per the official UPSC answer key.
Consider the following statements :
- 1. Jhelum River passes through Wular Lake.
- 2. Krishna River directly feeds Kolleru Lake.
- 3. Meandering of Gandak River formed Kanwar Lake.
How many of the statements given above are correct?
Answer (a) & explanation
Only one statement is correct (a). Statement 1 is right: the Jhelum flows into and out of Wular Lake in north Kashmir, India's largest freshwater lake, which acts as a flood basin for the river. Statement 2 is wrong: Kolleru Lake in Andhra Pradesh lies between the Godavari and Krishna deltas, but it is fed by seasonal streams such as the Budameru and Tammileru and by delta channels, not directly by the Krishna. Statement 3 is wrong: Kanwar Lake (Kabartal) in Begusarai, Bihar, is an oxbow wetland formed by the meandering of the Burhi Gandak, not the Gandak.
Notice that Kanwar became Bihar's first Ramsar site in 2020. Kolleru is also a Ramsar wetland, long damaged by illegal fish tanks.
Gandak and Burhi Gandak are two different rivers. Statement 3 picks the wrong one.
Answer as per the official UPSC answer key.
Which one of the following statements best reflects the Chief purpose of the 'Constitution' of a country?
Answer (c) & explanation
A Constitution chiefly defines and limits government's powers (c). Every option is something a Constitution does, but the chief purpose is to set out the powers of government and put limits on them. That is what makes a government constitutional, or limited, rather than all-powerful. This idea is called constitutionalism. Option (a) is a secondary task: it gives the goals for lawmaking, through the Preamble and Directive Principles. Option (b) is true but is only the first step. Option (d) is a goal of a welfare state, set by the Indian Constitution, but not the chief purpose of every Constitution.
Notice how India limits power: Fundamental Rights, judicial review, federalism, separation of powers and the basic structure doctrine from Kesavananda Bharati (1973).
four true statements. When UPSC writes "best" or "chief", look for the most basic idea, not the most attractive one.
Answer as per the official UPSC answer key.
With reference to coal-based thermal power plants in India, consider the following statements :
- 1. None of them uses seawater.
- 2. None of them is set up in water-stressed district.
- 3. None of them is privately owned.
How many of the above statements are correct?
Answer (d) & explanation
None of the statements is correct (d). Statement 1 is wrong: coastal plants such as those at Mundra in Gujarat and others on the Tamil Nadu and Andhra coasts use seawater for cooling. Statement 2 is wrong: studies have found many thermal plants in water-stressed districts, and some have shut for days in droughts for lack of water. Statement 3 is wrong: large coal plants are run by private companies such as Adani Power, Tata Power and JSW, besides public firms like NTPC. All three "none" statements fail.
Notice the hint: UPSC's absolute words like "none", "all" and "only" are often wrong. Coal still gives about 70–75% of India's power, and plants must meet stricter water-use and emission norms.
"none" statements are easy to sink with one example each.
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.
Consider the following heavy industries :
- 1. Fertilizer plants
- 2. Oil refineries
- 3. Steel plants
Green hydrogen is expected to play a significant role in decarbonizing how many of the above industries?
Answer (c) & explanation
Green hydrogen can help decarbonise all three (c). Item 1 is right: fertiliser plants use hydrogen to make ammonia, the base of urea. Item 2 is right: oil refineries use hydrogen to remove sulphur from fuels and to crack heavy oils. Both now mostly use grey hydrogen made from natural gas, which releases CO₂. Switching to green hydrogen, made from water using renewable power, cuts those emissions. Item 3 is right: steel plants can use hydrogen in place of coking coal to remove oxygen from iron ore, called direct reduced iron, leaving water instead of CO₂.
Notice India's National Green Hydrogen Mission (2023) with its SIGHT incentive programme. Sweden's HYBRIT project made the first fossil-free steel, and Indian steelmakers are running pilots.
Answer as per the official UPSC answer key.
Each digit of a 9-digit number is 1. It is multiplied by itself. What is the sum of the digits of the resulting number ?
Answer (c) & explanation
The digit sum is 81 (c). Step 1: 111111111 × 111111111 = 12345678987654321. Step 2: add the digits: 2 × (1 + 2 + ... + 8) + 9 = 2 × 36 + 9 = 81. Step 3: so the answer is (c). Option (a), 64, is 8², the result for eight ones. Options (b) and (d) are guesses.
Tip: for a number made of n ones (n up to 9), the square reads 1, 2, ..., n, ..., 2, 1. Its digit sum is simply n². Here 9² = 81.
Answer as per the official UPSC answer key.
For five children with ages a < b < c < d < e; any two successive ages differ by 2 years.
Question: What is the age of the youngest child ?
Statement-1: The age of the eldest is 3 times the youngest.
Statement-2: The average age of the children is 8 years.
Which one of the following is correct in respect of the above Question and the Statements ?
Answer (b) & explanation
Either statement alone is enough (b). Step 1: the ages go up by 2 each time: a, a + 2, a + 4, a + 6, a + 8. Step 2: Statement-1: the eldest is 3 times the youngest. So a + 8 = 3a, giving a = 4. Step 3: Statement-2: the average is 8. The average of five equally spaced ages is the middle one, a + 4 = 8, so a = 4. Each works alone. Options (a), (c) and (d) fail.
Tip: for equally spaced numbers, the average is the middle term. This saves time in many sequence questions.
Answer as per the official UPSC answer key.
Consider the following statements :
- Statement-I : Marsupials are not naturally found in India.
- Statement-II : Marsupials can thrive only in montane grasslands with no predators.
Which one of the following is correct in respect of the above statements?
Answer (c) & explanation
Statement I is correct but Statement II is wrong (c). Statement I is right: marsupials, pouched mammals such as kangaroos, live naturally only in Australia, New Guinea and the Americas, so none are native to India. Statement II is wrong: marsupials live in deserts, forests, wetlands and grasslands, often with predators; the opossum thrives in American towns. Their absence from India is a matter of history: Australia broke away from Gondwana early, and its marsupials evolved in isolation, while placental mammals came to dominate elsewhere.
Notice the term endemism: species found in only one region because of past isolation. India's own endemics, such as the lion-tailed macaque, are concentrated in the Western Ghats, a biodiversity hotspot.
Answer as per the official UPSC answer key.
Which one of the following explains the practice of ‘Vattakirutal’ as mentioned in Sangam poems?
Answer (d) & explanation
Vadakkiruttal was a defeated king's ritual fast to death (d). Vadakkiruttal, "sitting facing north", was a ritual fast unto death by a king or warrior who had been defeated or shamed. The best-known case is the Chola king Kopperuncholan, who chose it after a quarrel with his sons; his friend, the poet Pisirandaiyar, joined him. Puram poems record it as an honourable death. Option (a) is wrong: there is no such term for women bodyguards. Option (b) describes the poets' Sangam assemblies. Option (c) describes girls guarding millet fields, a theme of the kurinji poems.
Notice the parallel with the Jain practice of sallekhana, a ritual fast to death, which Chandragupta Maurya is said to have taken at Shravanabelagola.
Answer as per the official UPSC answer key.
Consider the following statements :
- 1. According to the Constitution of India, the Central Government has a duty to protect States from internal disturbances.
- 2. The Constitution of India exempts the States from providing legal counsel to a person being held for preventive detention.
- 3. According to the Prevention of Terrorism Act, 2002, confession of the accused before the police cannot be used as evidence.
How many of the above statements are correct?
Answer (b) & explanation
Two statements are correct (b). Statement 1 is right: Article 355 makes it the Union's duty to protect every State against external aggression and internal disturbance, and to ensure it is run according to the Constitution. Statement 2 is right: Article 22(3) says the rights to be told the grounds of arrest, to consult a lawyer and to be produced before a magistrate do not apply to preventive detention. Statement 3 is wrong: POTA did the opposite: confessions made to senior police officers (SP rank and above) could be used as evidence, which drew much criticism.
Notice that under normal law, the Evidence Act (now the Bharatiya Sakshya Adhiniyam, 2023) makes confessions to the police inadmissible. POTA was repealed in 2004.
POTA was controversial exactly because it made police confessions admissible. The ordinary rule (no police confessions) did not apply.
Answer as per the official UPSC answer key.
What is the remainder when 85 × 87 × 89 × 91 × 95 × 96 is divided by 100 ?
Answer (a) & explanation
The remainder is 0 (a). Step 1: 100 = 4 × 25. Step 2: 85 = 5 × 17 and 95 = 5 × 19 give two 5s, so the product has 5 × 5 = 25. 96 = 32 × 3 gives plenty of 2s, so 4 also divides it. Step 3: so the product is a multiple of 4 × 25 = 100. The remainder is 0. Options (b), (c) and (d) assume something is left over.
Tip: to divide by 100, check for two 5s and two 2s among the factors. If both are there, the remainder is zero.
Answer as per the official UPSC answer key.
Consider the following including the Question and the Statements :
There are 5 members A, B, C, D, E in a family.
Question : What is the relation of E to B?
Statement-1 : A and B are a married couple.
Statement-2 : D is the father of C.
Statement-3 : E is D's son.
Statement-4 : A and C are sisters.
Which one of the following is correct in respect of the above Question and Statements?
Answer (c) & explanation
All four statements together are sufficient (c). Step 1: statements 2 and 4: D is C's father, and A is C's sister. So D is A's father too. Step 2: statement 3: E is D's son, so E is A's brother. Step 3: statement 1: B is married to A. So E is B's brother-in-law. Each statement is needed: without 2 or 4 we cannot link A to D; without 3 we know nothing of E; without 1 we know nothing of B. Options (a), (b) and (d) fail.
Tip: build a small family tree as you read each statement. Then test each option by removing one statement.
Option (b) leaves out D being C's father, so A cannot be tied to D and E.
Answer as per the official UPSC answer key.
Read the passage
In India, while the unemployment rate is a frequently used measure of poor performance of the economy, under conditions of rising school and college enrolment, it paints an inaccurate picture. The reported unemployment rate is dominated by the experience of younger Indians who face higher employment challenges and exhibit greater willingness to wait for the right job than their older peers. The unemployment challenge is greater for people with secondary or higher education, and rising education levels inflate unemployment challenges.
Which one of the following statements most likely reflects as to what the author of the passage intends to say ?
Answer (b) & explanation
The author says unemployment should be seen in light of rising education and aspirations of young Indians (b). Step 1: the passage says the unemployment rate paints an inaccurate picture when school and college enrolment are rising. Step 2: young, educated Indians are more willing to "wait for the right job", and rising education "inflates" unemployment. So it reflects education and aspirations. That is (b). Step 3: option (a), quality of education, and option (c), labour-intensive industry, are not discussed. Option (d), self-employment, is not suggested.
Tip: this is "aspirational unemployment". Educated youth may wait for a suitable job rather than take any job.
Answer as per the official UPSC answer key.
Consider the following statements :
- Statement-I : Carbon markets are likely to be one of the most widespread tools in the fight against climate change.
- Statement-II : Carbon markets transfer resources from the private sector to the State.
Which one of the following is correct in respect of the above statements?
Answer (b) & explanation
Both statements are correct but II does not explain I (b). Statement I is right: carbon markets put a price on emissions and are spreading fast, from the EU's ETS to China's national market, and the Article 6 rules under the Paris Agreement. Statement II is right: under cap-and-trade, governments sell or auction emission permits, so money moves from companies to the State. But II is not the reason for I: markets spread because they cut emissions where it is cheapest, letting firms that can cut cheaply sell their spare permits.
Notice India's own Carbon Credit Trading Scheme (2023), run by the Bureau of Energy Efficiency. It sets emission-intensity targets for heavy industries such as cement, steel and aluminium.
Answer as per the official UPSC answer key.
Consider the following pairs :
| Objects in space | Description
| 1. Cepheids | Giant clouds of dust and gas in space
| 2. Nebulae | Stars which brighten and dim periodically
| 3. Pulsars | Neutron stars that are formed when massive stars run out of fuel and collapse
How many of the above pairs are correctly matched?
Answer (a) & explanation
Only one pair is correct (a). Pair 3 is right: pulsars are fast-spinning neutron stars, left when a massive star runs out of fuel and collapses in a supernova; they send out beams of radio waves like a lighthouse. Pairs 1 and 2 are swapped. Cepheids are pulsating stars that brighten and dim regularly; their period shows their true brightness, so they are used to measure cosmic distances. Nebulae are giant clouds of dust and gas, where new stars are born.
Notice that Henrietta Leavitt found the Cepheid period-brightness rule, and Edwin Hubble used it to show the universe is expanding. India's GMRT near Pune helps study pulsars, which act as precise cosmic clocks.
Answer as per the official UPSC answer key.
Consider the following statements :
The 'Stability and Growth Pact' of the European Union is a treaty that
- 1. limits the levels of the budgetary deficit of the countries of the European Union
- 2. makes the countries of the European Union to share their infrastructure facilities
- 3. enables the countries of the European Union to share their technologies
How many of the above statements are correct?
Answer (a) & explanation
Only one statement is correct (a). Statement 1 is right: the Stability and Growth Pact (1997) is a set of fiscal rules for EU members: the budget deficit should stay below 3% of GDP and public debt below 60% of GDP. Countries that break the rules face an excessive deficit procedure. Statement 2 is wrong: it says nothing about sharing infrastructure. Statement 3 is wrong: it says nothing about sharing technology.
Notice that the rules were suspended during COVID-19 and reformed in 2024, giving countries more time to cut debt. The aim is to keep the euro stable, since members share a currency but run their own budgets. India's version is the FRBM Act, 2003, which sets fiscal deficit targets for the Centre.
Answer as per the official UPSC answer key.
125 identical cubes are arranged in the form of a cubical block. How many cubes are surrounded by other cubes from each side?
Answer (a) & explanation
27 cubes are surrounded on every side (a). Step 1: 125 = 5 × 5 × 5, so the block is 5 cubes on each side. Step 2: a cube with neighbours on all six sides cannot be on the outer surface. Remove one layer from each face. Step 3: the inside block is (5 − 2) × (5 − 2) × (5 − 2) = 3 × 3 × 3 = 27. Options (b), (c) and (d) miscount.
Tip: for an n × n × n cube, the hidden inner cubes are (n − 2)³. The cubes with paint on just one face are 6(n − 2)².
Answer as per the official UPSC answer key.
There are three traffic signals. Each signal changes colour from green to red and then from red to green. The first signal takes 25 seconds, the second signal takes 39 seconds and the third signal takes 60 seconds to change the colour from green to red. The durations for green and red colours are same. At 2:00 p.m., they together turn green. At what time will they change to green next, simultaneously ?
Answer (b) & explanation
They turn green together again at 4:10 p.m. (b). Step 1: green and red last the same time. So each full cycle is double: 50 s, 78 s and 120 s. Step 2: LCM of 50, 78 and 120 = 2³ × 3 × 5² × 13 = 7800 s = 130 minutes. Step 3: 2:00 p.m. + 2 hours 10 minutes = 4:10 p.m. Option (a), 4:00 p.m., uses wrong cycles. Options (c) and (d) miscalculate.
Tip: always use the full cycle (green + red) for "turn green again". Using only the green time is the common trap.
LCM of 25, 39 and 60 gives the next time they all change, not the next time they all turn green.
Answer as per the official UPSC answer key.