UPSC Prelims PYQs with explanations
Real questions from official papers, mapped to syllabus topics. Attempt each one; the answer and the reason appear instantly.
A has some coins. He gives half of the coins and 2 more to B. B gives half of the coins and 2 more to C. C gives half of the coins and 2 more to D. The number of coins D has now, is the smallest two-digit number. How many coins does A have in the beginning?
Answer (d) & explanation
A had 52 coins at the start (d). Step 1: the smallest two-digit number is 10, so D has 10. Work backwards. Step 2: D got half of C's coins plus 2. So half of C's coins = 8, and C had 16. Step 3: C got half of B's plus 2, so half of B's = 14 and B had 28. B got half of A's plus 2, so half of A's = 26 and A had 52. Options (a), (b) and (c) fail this check.
Tip: when a chain of "half plus 2" ends at a known number, reverse each step: subtract 2, then double.
Answer as per the official UPSC answer key.
When 70% of a number x is added to another number y, the sum becomes 165% of the value of y. When 60% of the number x is added to another number z, then the sum becomes 165% of the value of z. Which one of the following is correct?
Answer (a) & explanation
The order is z < x < y (a). Step 1: 70% of x + y = 165% of y. So 70% of x = 65% of y. A bigger share of x equals a smaller share of y, so y is bigger than x. Step 2: 60% of x + z = 165% of z. So 60% of x = 65% of z. A bigger share of z equals a smaller share of x, so z is smaller than x. Step 3: together: z < x < y. Options (b), (c) and (d) get the order wrong.
Tip: if a% of P = b% of Q and a is larger than b, then P is smaller than Q. The number taking the bigger percentage is the smaller one.
Answer as per the official UPSC answer key.
With reference to India, consider the following statements :
- 1. Government law officers and legal firms are recognised as advocates, but corporate lawyers and patent attorneys are excluded from recognition as advocates.
- 2. Bar Councils have the power to lay down the rules relating to legal education and recognition of law colleges.
Which of the statements given above is/are correct?
Answer (b) & explanation
Only statement 2 is correct (b). Statement 1 is wrong: under the Advocates Act, 1961, only individuals enrol as advocates, so a law firm is not an advocate. Also, corporate lawyers and patent attorneys who are enrolled are not excluded from being advocates. Statement 2 is right: under Section 7 of the Act, the Bar Council of India sets standards of legal education and recognises universities and law colleges whose degrees qualify a person to enrol.
Notice the structure: the Bar Council of India at the top and State Bar Councils below. Since 2010, new law graduates must pass the All India Bar Examination to practise. In 2023, the BCI allowed foreign law firms to practise non-litigation work in India.
one wrong word ("legal firms") inside a long statement that is otherwise plausible.
Answer as per the official UPSC answer key.
With reference to polyethylene terephthalate, the use of which is so widespread in our daily lives, consider the following statements :
- 1. Its fibres can be blended with wool and cotton fibres to reinforce their properties.
- 2. Containers made of it can be used to store any alcoholic beverage.
- 3. Bottles made of it can be recycled into other products.
- 4. Articles made of it can be easily disposed of by incineration without causing greenhouse gas emissions.
Which of the statements given above are correct ?
Answer (a) & explanation
Statements 1 and 3 are correct (a). Polyethylene terephthalate (PET) is the plastic of water and soft-drink bottles. Statement 1 is right: as a fibre it is polyester, often blended with cotton and wool to add strength and resist creasing. Statement 3 is right: PET bottles are widely recycled into fibre, carpets and new bottles. Statement 2 is wrong: it is not suited to storing every alcoholic drink; long storage of strong spirits can draw out chemicals. Statement 4 is wrong: burning PET releases CO₂ and other pollutants.
Notice that India recycles a high share of its PET bottles, much of it into polyester fibre. The Plastic Waste Management Rules (amended 2022) ban many single-use plastics and set EPR targets for producers.
Answer as per the official UPSC answer key.
With reference to the "Tea Board" in India, consider the following statements :
- 1. The Tea Board is a statutory body.
- 2. It is a regulatory body attached to the Ministry of Agriculture and Farmers Welfare.
- 3. The Tea Board's Head Office is situated in Bengaluru.
- 4. The Board has overseas offices at Dubai and Moscow.
Which of the statements given above are correct ?
Answer (d) & explanation
Statements 1 and 4 are correct (d). Statement 1 is right: the Tea Board was set up under the Tea Act, 1953, so it is a statutory body. Statement 4 is right: it keeps overseas offices in Dubai and Moscow to promote Indian tea in key markets. Statement 2 is wrong: like the Coffee, Rubber and Spices boards, it works under the Ministry of Commerce and Industry, because these are export crops, not under the Agriculture Ministry. Statement 3 is wrong: its head office is in Kolkata; it is the Coffee Board that sits in Bengaluru.
Notice the other boards: the Spices Board is in Kochi and the Rubber Board in Kottayam. The commodity boards have long been under review for merger and reform.
plantation crops are farm products, but their Boards sit with Commerce. Bengaluru belongs to the Coffee Board.
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Answer as per the official UPSC answer key.
Which date of June 2099 among the following is Sunday?
Answer (d) & explanation
1. Use a known day as an anchor: 1 January 2001 was a Monday. From 1 Jan 2001 to 1 Jan 2099 is 98 years, with 24 leap years (2004 to 2096). Odd days = 98 + 24 = 122, which leaves 3 on division by 7. So 1 January 2099 is Thursday.
2. January to May 2099 (not a leap year) = 31 + 28 + 31 + 30 + 31 = 151 days, which leaves 4. So 1 June 2099 is Thursday + 4 = Monday.
3. 1 June is Monday, so 7 June is Sunday.
Answer as per the official UPSC answer key.
Three Statements followed by three Conclusions are given below. You have to take the Statements to be true even if they seem to be at variance from the commonly known facts. Read all the Conclusions and then decide which of the given Conclusions logically follows/follow from the Statements, disregarding the commonly known facts :
Statement-1 : Some doctors are teachers.
Statement-2 : All teachers are engineers.
Statement-3 : All engineers are scientists.
Conclusion-I : Some scientists are doctors.
Conclusion-II : All engineers are doctors.
Conclusion-III : Some engineers are doctors.
Which one of the following is correct?
Answer (c) & explanation
Conclusions I and III follow (c). Step 1: some doctors are teachers. All teachers are engineers, so those doctors are also engineers. Step 2: all engineers are scientists, so those doctors are also scientists. So "some engineers are doctors" (III) and "some scientists are doctors" (I) follow. Step 3: "all engineers are doctors" (II) does not follow; only some are. So options (a), (b) and (d) fail.
Tip: follow the small "some" group through each "all" statement. Wherever it goes, a "some" conclusion follows.
Answer as per the official UPSC answer key.
Read the passage
To encourage research is one of the functions of a university. Contemporary universities have encouraged research, not only in those cases where research is necessary, but on all sorts of entirely unprofitable subjects as well. Scientific research is probably never completely valueless. However silly and insignificant it may seem, however mechanical and unintelligent the labours of the researchers, there is always a chance that the results may be of value to the investigator of talent, who can use the facts collected for him by uninspired but industrious researchers as the basis of some fruitful generalization. But where research is not original, but consists in the mere rearrangement of existing materials, where its object is not scientific but literary or historical, then there is a risk of the whole business becoming merely futile.
The author’s assumption about scientific research is that
Answer (c) & explanation
The author assumes scientific research is never without some value (c). Step 1: the passage says scientific research is "probably never completely valueless". That means it always has some value. That is (c). Step 2: option (d) says it is always very valuable, which inflates "some value". Step 3: option (a), never very valuable, and option (b), sometimes very valuable, are not what the author says.
Tip: "never completely valueless" = "always has some value". Keep the strength of the claim exactly as the passage puts it.
Answer as per the official UPSC answer key.
Consider the following pairs :
| Peak | Mountains
| 1. Namcha Barwa | Garhwal Himalaya
| 2. Nanda Devi | Kumaon Himalaya
| 3. Nokrek | Sikkim Himalaya
Which of the pairs given above is/are correctly matched ?
Answer (b) & explanation
Only pair 2 is correct (b). Pair 1 is wrong: Namcha Barwa is the eastern anchor of the Himalaya, in Tibet, where the Tsangpo (Brahmaputra) makes its great bend around it; it is not in the Garhwal Himalaya. Pair 2 is right: Nanda Devi, India's second-highest peak, is in the Kumaon Himalaya of Uttarakhand. Pair 3 is wrong: Nokrek is the highest peak of the Garo Hills in Meghalaya, not in the Sikkim Himalaya, and it is a biosphere reserve.
Notice the divisions of the Himalaya by rivers: Punjab (Indus–Sutlej), Kumaon (Sutlej–Kali), Nepal (Kali–Teesta) and Assam (Teesta–Dihang). Nanga Parbat anchors the west. China plans a huge dam on the Tsangpo near Namcha Barwa.
Answer as per the official UPSC answer key.
With reference to Indian history, who of the following were known as “Kulah-Daran” ?
Answer (d) & explanation
The Sayyids were the Kulah-Daran (d). In the Delhi Sultanate, the Sayyids, who claimed descent from the Prophet through his daughter Fatima, were called kulah-daran, or "cap-wearers", after the pointed cap they wore as a mark of their status. They got respect, land grants and stipends at court. Option (b) is wrong: Qalandars were wandering dervishes who shaved their heads and rejected such marks of rank. Arab merchants (a) and Persian calligraphists (c) had no such title.
Notice how social rank worked in the Sultanate. Nobles were the ashraf, the commoners ajlaf, and religious men the ulama. Do not confuse these Sayyids with the Sayyid dynasty (1414–1451) of Khizr Khan, which ruled Delhi after Timur's invasion.
Answer as per the official UPSC answer key.
Certain species of which one of the following organisms are well known as cultivators of fungi ?
Answer (a) & explanation
Ants are well-known fungus farmers (a). Leafcutter ants of Central and South America cut pieces of leaves and carry them home. They do not eat the leaves; they use them to grow a fungus in underground gardens, and the fungus is their food. They even weed the garden and use bacteria that make antifungal chemicals to protect it. This is one of nature's oldest forms of agriculture, about 50 million years old. Cockroaches (b), crabs (c) and spiders (d) do not farm fungi.
Notice that some termites and ambrosia beetles also farm fungi, but neither is offered here. UPSC likes such symbiosis facts, like the fig and fig wasp, lichens (fungus plus alga) and mycorrhiza (fungus plus plant roots).
Answer as per the official UPSC answer key.
How many 3-digit natural numbers (without repetition of digits) are there such that each digit is odd and the number is divisible by 5 ?
Answer (b) & explanation
There are 12 such numbers (b). Step 1: a number divisible by 5 ends in 0 or 5. Since every digit must be odd, the last digit must be 5. Step 2: the first two digits come from the other odd digits: 1, 3, 7, 9. No repeats allowed. Step 3: the first digit has 4 choices and the second has 3. So 4 × 3 = 12. Option (a), 8, and the larger options (c) 16 and (d) 24 miscount.
Tip: fill the most restricted place first (here, the last digit). Then count the choices for the rest.
Answer as per the official UPSC answer key.
Six lectures A, B, C, D, E and F, each of one hour duration, are scheduled between 8:00 a.m. and 2:00 p.m.
Consider the Question and two Statements given below :
Question : Which lecture is in the third period?
Statement-1 : Lecture F is preceded by A and followed by C.
Statement-2 : There is no lecture after lecture B.
Which one of the following is correct in respect of the Question and the Statements?
Answer (d) & explanation
Even both statements are not enough (d). Step 1: Statement-2 says no lecture comes after B, so B is in the 6th period. Step 2: Statement-1 says A, F and C come one after another as a block A–F–C. This block sits somewhere in periods 1 to 5, along with D and E. Step 3: the block can start in period 1, 2 or 3. So the third period could hold C, F or A. It cannot be fixed. Options (a), (b) and (c) fail.
Tip: "preceded by A and followed by C" makes a fixed block. Count how many places the block can slide into.
Answer as per the official UPSC answer key.
With reference to the Indian economy, consider the following statements :
- 1. An increase in Nominal Effective Exchange Rate (NEER) indicates the appreciation of rupee.
- 2. An increase in the Real Effective Exchange Rate (REER) indicates an improvement in trade competitiveness.
- 3. An increasing trend in domestic inflation relative to inflation in other countries is likely to cause an increasing divergence between NEER and REER.
Which of the above statements are correct ?
Answer (c) & explanation
Statements 1 and 3 are correct (c). Statement 1 is right: NEER (Nominal Effective Exchange Rate) is a weighted average of the rupee against a basket of trading partners' currencies; a rise means the rupee has appreciated. Statement 2 is wrong: REER adjusts NEER for inflation differences. A rising REER means Indian goods are getting dearer abroad, so competitiveness falls, not improves. Statement 3 is right: if India's inflation runs higher than its partners', REER rises even when NEER does not, so the two drift apart.
Notice that the RBI publishes NEER and REER on 40-currency and 6-currency baskets. A REER above 100 suggests the rupee is overvalued against the base year.
statement 2 reverses the effect. A stronger real rupee hurts exporters; it does not help them.
Answer as per the official UPSC answer key.
Consider the following communication technologies :
- 1. Closed-circuit Television
- 2. Radio Frequency Identification
- 3. Wireless Local Area Network
Which of the above are considered Short-Range devices/technologies ?
Answer (d) & explanation
All three are short-range technologies (d). Short-Range Devices (SRDs) are low-power radio transmitters that work over short distances and have little potential to interfere with other services. Item 1 is right: wireless CCTV links send video over short ranges. Item 2 is right: RFID tags, used in FASTag and shop security, are read from close range. Item 3 is right: Wireless LAN, or Wi-Fi, covers a home or office. Bluetooth, NFC, wireless alarms and car remotes are other SRDs.
Notice that the Department of Telecommunications delicenses many SRD bands, such as parts of the 2.4 GHz and 5 GHz bands for Wi-Fi, so no licence is needed. In 2024, it delicensed the lower 6 GHz band for Wi-Fi.
Answer as per the official UPSC answer key.
With reference to Non-Fungible Tokens (NFTs), consider the following statements :
- 1. They enable the digital representation of physical assets.
- 2. They are unique cryptographic tokens that exist on a blockchain.
- 3. They can be traded or exchanged at equivalency and therefore can be used as a medium of commercial transactions.
Which of the statements given above are correct ?
Answer (a) & explanation
Statements 1 and 2 are correct (a). Statement 2 is right: a Non-Fungible Token is a unique cryptographic token recorded on a blockchain, such as Ethereum. Statement 1 is right: an NFT can stand for ownership of digital art, music, game items, or even physical assets like property or luxury goods. Statement 3 is wrong: non-fungible means no two tokens are alike, so they cannot be swapped at par. That is why NFTs cannot work as money, unlike rupees or Bitcoin, which are fungible: any one unit equals any other.
Notice the tax angle: India treats NFTs and crypto as virtual digital assets, with a flat 30% tax on gains and 1% TDS on transfers since 2022. The RBI's own digital currency is the e-rupee.
statement 3 describes fungible tokens. The name itself tells you NFTs are not equivalent to each other.
Answer as per the official UPSC answer key.
Consider the following statements :
- 1. A bill amending the Constitution requires a prior recommendation of the President of India.
- 2. When a Constitution Amendment Bill is presented to the President of India, it is obligatory for the President of India to give his/her assent.
- 3. A Constitution Amendment Bill must be passed by both the Lok Sabha and the Rajya Sabha by a special majority and there is no provision for joint sitting.
Which of the statements given above are correct?
Answer (b) & explanation
Statements 2 and 3 are correct (b). Statement 1 is wrong: under Article 368, a Constitution Amendment Bill can be introduced in either House by a minister or a private member, without the President's prior recommendation. Statement 2 is right: since the 24th Amendment (1971), the President must give assent to an amendment Bill and cannot withhold it or return it. Statement 3 is right: each House must pass it separately by a special majority, and there is no joint sitting if they disagree.
Notice that amendments touching federal matters, such as the election of the President or the Seventh Schedule, also need ratification by half the State legislatures. The basic structure doctrine limits all amendments.
"prior recommendation" is needed for Money Bills and Bills on State boundaries (Article 3), not for amendments.
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Answer as per the official UPSC answer key.
In the series AABABCABCDABCDE..., which letter appears at the 100th place?
Answer (c) & explanation
The 100th letter is I (c). Step 1: the series is in groups: A, AB, ABC, ABCD and so on. Group n has n letters. Step 2: the first 13 groups fill 1 + 2 + ... + 13 = 13 × 14 ÷ 2 = 91 places. Step 3: group 14 starts at place 92. Place 100 is the 9th letter of that group, which is I. Options (a) G, (b) H and (d) J are one or two places off.
Tip: the sum of the first n numbers is n(n + 1)/2. It quickly tells you which group a position falls in.
Answer as per the official UPSC answer key.
Read the passage
The majority of people who fail to accumulate money sufficient for their needs, are generally, easily influenced by the opinions of others. They permit the newspapers and the gossiping neighbours to do their thinking for them. Opinions are the cheapest commodities on the earth. Everyone has a flock of opinions ready to be wished upon by anyone who will accept them. If you are influenced by opinions when you reach decisions, you will not succeed in any undertaking.
Which one of the following is implied by the passage?
Answer (c) & explanation
The passage implies there are people who fail to save enough money for their needs (c). Step 1: it begins: "The majority of people who fail to accumulate money..." This assumes such people exist. That is (c). Step 2: option (a) says most people do not save. But the passage speaks of the majority of those who fail, not most people overall. Step 3: option (b) says most people never fail, which the passage does not say. Option (d), no need to save, goes against it.
Tip: an implication can hide in the subject of a sentence. "The majority of X" quietly assumes X exists.
Answer as per the official UPSC answer key.
Consider the following statements :
- 1. The Constitution of India classifies the ministers into four ranks viz. Cabinet Minister, Minister of State with Independent Charge, Minister of State and Deputy Minister.
- 2. The total number of ministers in the Union Government, including the Prime Minister, shall not exceed 15 percent of the total number of members in the Lok Sabha.
Which of the statements given above is/are correct?
Answer (b) & explanation
Only statement 2 is correct (b). Statement 1 is wrong: the Constitution speaks only of a "Council of Ministers". The ranks of Cabinet Minister, Minister of State (Independent Charge), Minister of State and Deputy Minister come from practice, not from the Constitution. The word "Cabinet" appears only once, in Article 352, added by the 44th Amendment (1978). Statement 2 is right: Article 75(1A), added by the 91st Amendment (2003), caps the Council of Ministers at 15% of the Lok Sabha's total strength, Prime Minister included.
Notice that the 91st Amendment also set a minimum of 12 ministers in States, and barred defectors disqualified under the Tenth Schedule from becoming ministers.
Answer as per the official UPSC answer key.