UPSC Prelims PYQs with explanations
Real questions from official papers, mapped to syllabus topics. Attempt each one; the answer and the reason appear instantly.
In the English alphabet, the first 4 letters are written in opposite order; and the next 4 letters are written in opposite order and so on; and at the end Y and Z are interchanged. Which will be the fourth letter to the right of the 13th letter ?
Answer (b) & explanation
The letter is T (b). Step 1: reverse the alphabet in blocks of four: DCBA HGFE LKJI PONM TSRQ XWVU. Then Y and Z swap, giving ZY at the end. Step 2: count to the 13th letter. The first three blocks have 12 letters, so the 13th is the first letter of the 4th block: P. Step 3: the fourth letter to the right of the 13th is the 17th letter. That is the first letter of the 5th block: T. Option (a), N, comes from the normal alphabet. Options (c) and (d) are other miscounts.
Tip: write out the new order fully before counting. "Fourth to the right of the 13th" simply means position 13 + 4 = 17.
Answer as per the official UPSC answer key.
Read the passage
“...... most people would agree that telling deliberate lies is wrong, except perhaps in certain special situations where more harm will be done by telling the truth. Even the most truthful people probably tell a good many more lies that might be regarded as semantic lies; their use of words contains some measure of falsehood, more or less deliberate.”
The idea which the first part of the passage mentions is
Answer (d) & explanation
UPSC's key gives (d): disagreement about the harm in telling the truth. Step 1: the first part says most people agree deliberate lies are wrong, "except perhaps in certain special situations where more harm will be done by telling the truth". Step 2: UPSC reads the key idea as this exception: people differ on when telling the truth does harm. That is (d). Step 3: option (a), agreement about telling lies, also looks close because of "most people would agree". But UPSC picked the exception as the idea. Options (b) and (c) do not match the wording.
Tip: in short quotes, UPSC often tests the qualifier ("except", "unless"). The exception usually carries the idea being examined.
Answer as per the official UPSC answer key.
With reference to the ‘New York Declaration on Forests’, which of the following statements are correct?
- 1. It was first endorsed at the United Nations Climate Summit in 2014.
- 2. It endorses a global timeline to end the loss of forests.
- 3. It is a legally binding international declaration.
- 4. It is endorsed by governments, big companies and indigenous communities.
- 5. India was one of the signatories at its inception.
Select the correct answer using the code given below.
Answer (a) & explanation
Statements 1, 2 and 4 are correct (a). Statement 1 is right: the New York Declaration on Forests came out of the UN Climate Summit in September 2014. Statement 2 is right: it set a global timeline to halve natural forest loss by 2020 and end it by 2030. Statement 4 is right: it was endorsed by governments, big companies, NGOs and indigenous groups. Statement 3 is wrong: it is a voluntary, non-binding declaration. Statement 5 is wrong: India did not sign it at its launch.
Notice the later Glasgow Leaders' Declaration on Forests (COP26, 2021), which again pledged to end deforestation by 2030; India did not sign that either. Bonn Challenge targets land restoration.
"declaration" plus "legally binding" is a contradiction you can spot.
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Answer as per the official UPSC answer key.
Consider the following statements :
- 1. In the tropical zone, the western sections of the oceans are warmer than the eastern sections owing to the influence of trade winds.
- 2. In the temperate zone, westerlies make the eastern sections of oceans warmer than the western sections.
Which of the statements given above is/are correct?
Answer (c) & explanation
Both statements are correct (c). Statement 1 is right: in the tropics, the trade winds blow from east to west, piling warm surface water on the western side of oceans, while cold water upwells on the eastern side, near South America and Africa. Statement 2 is right: in temperate latitudes, the westerlies carry warm currents, such as the North Atlantic Drift, towards the eastern side of the oceans. That is why north-west Europe is mild in winter, while places at the same latitude in eastern Canada are frozen.
Notice that when the trade winds weaken, warm water moves east across the Pacific: that is El Niño, which often weakens India's monsoon. Cold eastern currents include the Humboldt and Benguela.
Answer as per the official UPSC answer key.
What was the exact constitutional status of India on 26th January, 1950?
Answer (b) & explanation
India was a Sovereign Democratic Republic (b). On 26 January 1950, the Preamble described India as a "Sovereign Democratic Republic". The words "Socialist" and "Secular" were added by the 42nd Amendment in 1976, during the Emergency, along with "integrity". So option (c) and option (d) describe India only after 1976. Option (a) is wrong because it leaves out "Sovereign", which was there from the start.
Notice that the Preamble is based on Nehru's Objectives Resolution (13 December 1946). The Supreme Court held it is part of the Constitution in Kesavananda Bharati (1973), after saying otherwise in the Berubari case (1960). In 2024, the Court upheld the 1976 additions.
(d) is today's text. The question asks about 1950.
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Answer as per the official UPSC answer key.
Integers are listed from 700 to 1000. In how many integers is the sum of the digits 10 ?
Answer (d) & explanation
9 integers have a digit sum of 10 (d). Step 1: numbers from 700 to 799 are written 7ab. We need a + b = 3: 703, 712, 721, 730. That is 4. Step 2: 8ab needs a + b = 2: 802, 811, 820. That is 3. 9ab needs a + b = 1: 901, 910. That is 2. Step 3: 1000 has digit sum 1, so it does not count. Total = 4 + 3 + 2 = 9. Options (a), (b) and (c) miss some.
Tip: two digits adding to k (with k ≤ 9) can be arranged in k + 1 ways. So 3 gives 4, 2 gives 3, 1 gives 2.
Answer as per the official UPSC answer key.
Read the passage
The best universities like Harvard and MIT, despite having the luxury of having some truly excellent teachers on their payroll, are increasingly embracing the “flipped classroom” format, where students listen to video lectures at home, and spend class time applying their knowledge, solving problems, discussing examples, etc. Professors guide that discussion and fill in wherever necessary, explaining those bits that seem to be eluding the students and throwing in advanced ideas that happen to be topical. These universities have made their video lectures available free for anyone in the world. They are also encouraging colleges and universities all over the world to integrate these online courses into their own pedagogy, picking the pieces that are appropriate for their needs and building a package around them.
Which one of the following statements best reflects the central idea of the passage given above ?
Answer (b) & explanation
The central idea is that higher education can be made easier to access and cheaper without diluting content (b). Step 1: top universities like Harvard and MIT put their video lectures online free for anyone. Other colleges can build these into their teaching. So good content reaches more people at low cost. That is (b). Step 2: option (a) says online mode is better than classroom. But the flipped classroom mixes both: videos at home, discussion in class. Step 3: option (c), no need for infrastructure, and option (d), coaching institutes thriving, are not in the passage.
Tip: a "flipped classroom" means lectures at home and problem-solving in class. Don't confuse blended learning with fully online learning.
Answer as per the official UPSC answer key.
Which among the following steps is most likely to be taken at the time of an economic recession?
Answer (b) & explanation
Raising spending on public projects is the likely step (b). In a recession, demand is weak, factories cut output and jobs are lost. The government tries to add demand through expansionary fiscal policy. Spending more on public works such as roads, housing and irrigation creates jobs and incomes, and those incomes are spent again (the multiplier effect). Option (a) is wrong: it pairs a tax cut (expansionary) with a rate hike (contractionary). Option (c) is wrong: it pairs a tax hike (contractionary) with a rate cut (expansionary). Option (d) is plainly contractionary and would deepen the slump.
Notice Keynes, who argued for public spending in the Great Depression. India raised capital expenditure sharply after COVID to revive growth.
options (a) and (c) each contain one correct half. In a recession, both tax and interest should move down.
Answer as per the official UPSC answer key.
According to Portuguese writer Nuniz, the women in Vijayanagara Empire were expert in which of the following areas?
- 1. Wrestling
- 2. Astrology
- 3. Accounting
- 4. Soothsaying
Select the correct answer using the code given below.
Answer (d) & explanation
Nuniz described women in all four roles (d). Fernão Nuniz, a Portuguese horse trader in Vijayanagara around 1535, wrote that the palace women included wrestlers (item 1), astrologers (item 2), and soothsayers (item 4). He also wrote that women kept the accounts of expenses inside the palace (item 3), and that some served as clerks and even judges. So all four appear in his chronicle.
Notice the other foreign visitors to Vijayanagara: Domingo Paes (Portuguese, under Krishnadeva Raya), Abdur Razzaq (Persian, under Deva Raya II), and Niccolò de' Conti (Italian). The capital, Hampi, is a UNESCO World Heritage Site. The empire fell after the Battle of Talikota (1565).
Answer as per the official UPSC answer key.
Consider the following :
- 1. Bacteria
- 2. Fungi
- 3. Virus
Which of the above can be cultured in artificial/synthetic medium?
Answer (a) & explanation
Bacteria and fungi can be grown on artificial media (a). Item 1 is right: bacteria grow on nutrient agar or in broth, which supply sugars, salts and proteins. Item 2 is right: fungi also grow on artificial media, such as Sabouraud agar. Item 3 is wrong: viruses cannot reproduce on their own. They are not cells and have no machinery to make proteins, so they need living cells, such as cell cultures, embryonated eggs or animals. They cannot be grown on a cell-free synthetic medium.
Notice that most flu vaccines are still made by growing the virus in hens' eggs. The difference matters in medicine: antibiotics work against bacteria, not viruses. Bacteriophages are viruses that infect bacteria.
Answer as per the official UPSC answer key.
What is the position of the Right to Property in India?
Answer (b) & explanation
Property is a legal right available to any person (b). The 44th Amendment (1978) removed the right to property from Part III, the Fundamental Rights. It is now a constitutional (legal) right under Article 300A: "No person shall be deprived of his property save by authority of law." The word "person" covers non-citizens and companies too, not just citizens. So option (a) is wrong for limiting it to citizens. Options (c) and (d) are wrong: it is no longer a Fundamental Right, but it is still a legal right.
Notice that the right was once in Articles 19(1)(f) and 31. Because it is not a Fundamental Right, a person must go to a High Court under Article 226, not straight to the Supreme Court under Article 32.
"citizens only". Article 300A says "person".
Answer as per the official UPSC answer key.
A student appeared in 6 papers. The maximum marks are the same for each paper. His marks in these papers are in the proportion of 5 : 6 : 7 : 8 : 9 : 10. Overall he scored 60%. In how many number of papers did he score less than 60% of the maximum marks ?
Answer (b) & explanation
He scored below 60% in 3 papers (b). Step 1: the marks are in the ratio 5 : 6 : 7 : 8 : 9 : 10. Their average is 45 ÷ 6 = 7.5. Step 2: his overall score is 60%, and every paper has the same maximum. So the average share, 7.5, stands for 60%. Step 3: any paper with a ratio term below 7.5 is below 60%. Those are 5, 6 and 7, which is 3 papers. Options (a), (c) and (d) count wrongly. The papers with 8, 9 and 10 are above 60%.
Tip: when all papers carry the same maximum, the overall percentage equals the average paper. Simply compare each term with the average.
Answer as per the official UPSC answer key.
Read the passage
In our schools, we teach our children all that is there to know about physics, maths and history and what-have-you. But do we teach them about the bitter caste divide that plagues the country, about the spectre of famine that stalks large parts of our land, about gender sensitivity, about the possibility of atheism as a choice, etc. ? Equally important, do we teach them to ask questions, or do we teach them only to passively receive our wisdom ? From the cocooned world of school, suddenly, the adolescent finds himself/herself in the unfettered world of university. Here he/she is swept up in a turmoil of ideas, influences and ideologies. For someone who has been discouraged from asking questions and forming an opinion, this transition can be painful.
Which one of the following statements best reflects the central idea of the passage given above ?
Answer (d) & explanation
The central idea is that good citizens need social and life skills besides academic content (d). Step 1: the passage says schools teach physics, maths and history, but not caste, famine, gender or how to ask questions. Step 2: so the jump to university is painful. Schools must add life and social skills to subjects. That is (d). Step 3: option (a), curriculum versus parents' expectations, is not discussed. Option (b) contradicts the passage. Option (c) is too general; it misses the key point "in addition to academic content".
Tip: between a broad option and a specific one that matches the passage, choose the specific one. The best answer captures the passage's exact concern.
Answer as per the official UPSC answer key.
With reference to 'WaterCredit', consider the following statements :
- 1. It puts microfinance tools to work in the water and sanitation sector.
- 2. It is a global initiative launched under the aegis of the World Health Organization and the World Bank.
- 3. It aims to enable the poor people to meet their water needs without depending on subsidies.
Which of the statements given above are correct?
Answer (c) & explanation
Statements 1 and 3 are correct (c). WaterCredit was started by the non-profit Water.org, co-founded by Gary White and actor Matt Damon. Statement 1 is right: it puts microfinance tools to work, through partner lenders that give small loans to poor households for a tap connection or a toilet. Statement 3 is right: the idea is to help people meet water needs through credit they repay, not through subsidies. Statement 2 is wrong: it was not launched under the WHO or the World Bank.
Notice India's own water programmes: the Jal Jeevan Mission (2019), which aims at a tap connection for every rural home, and the Swachh Bharat Mission for toilets. SDG 6 covers clean water and sanitation.
Answer as per the official UPSC answer key.
With reference to Indian history, which of the following statements is/are correct?
- 1. The Nizamat of Arcot emerged out of Hyderabad State.
- 2. The Mysore Kingdom emerged out of Vijayanagara Empire.
- 3. Rohilkhand Kingdom was formed out of the territories occupied by Ahmad Shah Durrani.
Select the correct answer using the code given below.
Answer (b) & explanation
Only statement 2 is correct (b). Statement 1 is wrong: Arcot was the seat of the Nawabs of the Carnatic, a Mughal province; it was not a Nizamat carved out of Hyderabad, though the Nizam claimed overlordship. Statement 2 is right: the Wodeyars of Mysore began as Vijayanagara feudatories and became independent after 1565. Statement 3 is wrong: Rohilkhand was built by Ali Muhammad Khan Rohilla from Mughal lands in the 1740s, before Ahmad Shah Durrani's invasions; the Rohillas later allied with Durrani.
Notice that Haidar Ali took power in Mysore from the Wodeyars in 1761. The Third Battle of Panipat (1761) saw Durrani defeat the Marathas.
The Carnatic nawab was nominally under the Nizam, so 1 looks right. UPSC's key treats it as wrong.
Answer as per the official UPSC answer key.
Consider the following statements :
- 1. In India, there is no law restricting the candidates from contesting in one Lok Sabha election from three constituencies.
- 2. In 1991 Lok Sabha Election, Shri Devi Lal contested from three Lok Sabha constituencies.
- 3. As per the existing rules, if a candidate contests in one Lok Sabha election from many constituencies, his/her party should bear the cost of bye-elections to the constituencies vacated by him/her in the event of him/her winning in all the constituencies.
Which of the statements given above is/are correct?
No official answer (question dropped) & notes
UPSC dropped this question from evaluation, so no answer was scored. The likely trouble was statement 2: Devi Lal did contest from three Lok Sabha seats in 1991 (Sikar, Rohtak and Ferozepur), but the wording was disputed. The current law is clear. Statement 1 is wrong: since 1996, Section 33(7) of the Representation of the People Act, 1951 lets a candidate contest from at most two constituencies. Statement 3 is wrong: no rule makes the party pay for bye-elections; the Election Commission has only suggested that the candidate pay.
Notice that a winner of two seats must quit one within 14 days under Section 70. Before 1996, there was no limit on the number of seats.
UPSC did not evaluate this question, so no official answer exists. Use it for practice only.
UPSC dropped this question from evaluation; there is no official answer.
In a class, 60% of students are from India and 50% of the students are girls. If 30% of the Indian students are girls, then what percentage of foreign students are boys ?
Answer (d) & explanation
20% of foreign students are boys (d). Step 1: take 100 students. 60 are Indian, and 30% of them, 18, are girls. Step 2: total girls = 50, so foreign girls = 50 − 18 = 32. Foreign students = 100 − 60 = 40. So foreign boys = 40 − 32 = 8. Step 3: the question asks for a share of foreign students: 8 ÷ 40 = 20%. Option (a), 45%, and the others fail. Note 8% of the whole class is also a trap if you forget to divide by 40.
Tip: always check the base of the percentage. "Percentage of foreign students" means divide by the foreign total, not the class total.
"30% of the Indian students" is not 30% of the whole class.
Answer as per the official UPSC answer key.
Read the passage
Nothing can exist in a natural state which can be called good or bad by common assent, since every man who is in a natural state consults only his own advantage, and determines what is good or bad according to his own fancy and insofar as he has regard for his own advantage alone, and holds himself responsible to no one save himself by any law; and therefore sin cannot be conceived in a natural state, but only in a civil state, which is decreed by common consent what is good or bad, and each one holds himself responsible to the state.
Which one of the following statements best reflects the central idea of the passage given above ?
Answer (a) & explanation
The central idea is that ideas of right and wrong come from the formation of a state (a). Step 1: the passage says in a natural state each man judges good and bad by his own advantage. Nothing is good or bad "by common assent". Step 2: right and wrong are fixed by common consent "only in a civil state". That is (a). Step 3: option (b) says no man would be morally right without a ruler, which goes too far. Option (c) calls man immoral; but the passage says morality cannot even exist in a natural state. Option (d), survival of the species, is not discussed.
Tip: this is Spinoza's social-contract view. "Immoral" needs a moral standard; the passage says no shared standard exists before the state.
Answer as per the official UPSC answer key.
Read the passage
“...... most people would agree that telling deliberate lies is wrong, except perhaps in certain special situations where more harm will be done by telling the truth. Even the most truthful people probably tell a good many more lies that might be regarded as semantic lies; their use of words contains some measure of falsehood, more or less deliberate.”
Which one of the following habits is found more often in good people ?
Answer (b) & explanation
The habit found more often in good people is intentional mixing of truth with falsehood (b). Step 1: the passage says even the most truthful people tell "semantic lies". Their words contain "some measure of falsehood, more or less deliberate". Step 2: "deliberate" means intentional. So truth mixed with falsehood on purpose is (b). Step 3: option (a) leaves out the deliberate part. Options (c), falsifying facts, and (d), complete concealment, are much stronger than the passage's mild claim.
Tip: when two options look alike, find the word that separates them. Here "intentional" matches "deliberate" in the passage.
Answer as per the official UPSC answer key.
Magnetite particles, suspected to cause neurodegenerative problems, are generated as environmental pollutants from which of the following?
- 1. Brakes of motor vehicles
- 2. Engines of motor vehicles
- 3. Microwave stoves within homes
- 4. Power plants
- 5. Telephone lines
Select the correct answer using the code given below.
Answer (b) & explanation
Vehicle brakes, engines and power plants produce magnetite (b). Magnetite is a magnetic iron oxide. Its tiny nanoparticles come from combustion and friction. Item 1 is right: brake wear grinds off iron particles. Item 2 is right: vehicle engines release them in exhaust. Item 4 is right: burning coal and other fuels in power plants produces them. Items 3 and 5 are wrong: microwave ovens and telephone lines give off no such particles.
Notice the 2016 study (Maher and others) that found magnetite particles in human brain tissue and linked them to air pollution, raising concern about Alzheimer's disease. Such particles fall within PM2.5, which the National Clean Air Programme (2019) aims to reduce.
Answer as per the official UPSC answer key.