CSAT 2025

UPSC Prelims CSAT 2025 Solution

Access comprehensive UPSC CSAT 2025 Prelims solutions with detailed answer keys and step-by-step explanations.

Perfect for UPSC Civil Services Preliminary Examination candidates seeking to evaluate their CSAT 2025 performance and strengthen their preparation for future attempts. Our detailed solutions simplify complex problems and boost your confidence for the next stage of India’s premier competitive exam.

Ideal study resource for serious UPSC aspirants aiming to crack the Civil Services Aptitude Test and advance toward their civil services career goals.

UPSC Prelims CSAT 2025 Solution

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Q. A natural number N is such that it can be expressed as N = p + q + r, where p, q and r are distinct factors of N. How many numbers below 50 have this property?

Q. Three prime numbers p, q and r, each less than 20, are such that p – q = q – r. How many distinct possible values can we get for (p + q + r)?

Q. How many possible values of (p + q + r) are there satisfying 1/p + 1/q + 1/r = 1, where p, q and r are natural numbers (not necessarily distinct)?

Q. What comes at X and Y respectively in the following sequence? January, January, December, October, X, March, October, Y, September

Q. Team X scored a total of N runs in 20 overs. Team Y tied the score in 10% less overs. Had team Y’s average run rate (runs per over) been 50% higher, the scores would have been tied in 12 overs. How many runs were scored by team X?

Q. The price (p) of a commodity is first increased by k%; then decreased by k%; again increased by k%; and again decreased by k%. If the new price is q, then what is the relation between p and q?

Q. A solid cube is painted yellow on all its faces. The cube is then cut into 60 smaller but equal pieces by making the minimum number of cuts. Which of the following statements is/are correct?

Q. If 7 * 24 = 25 and 12 * 16 = 20, then what is 16 * 63 equal to?

Q. The petrol price shot up by 10% as a result of the hike in crude oil prices. The price of petrol before the hike was ₹90 per litre. A person travels 2200 km every month and his car gives a mileage of 16 km per litre. By how many km should he reduce his travel if he wants to maintain his expenditure at the previous level?

Q. A 4-digit number N is such that when divided by 3, 5, 6, 9 leaves a remainder 1, 3, 4, 7 respectively. What is the smallest value of N?

Q. Consider the following statements: I. If A < B > C < D > E > F ≥ G = H; then B is always greater than E.

Q. What is the unit digit in the multiplication of 1 × 3 × 5 × 7 × 9 × … × 999?

Q. Consider the first 100 natural numbers. How many of them are not divisible by any one of 2, 3, 5, 7 and 9?

Q. If 4 ≤ x ≤ 8 and 2 ≤ y ≤ 7, then what is the ratio of maximum value of (x + y) to minimum value of (x – y)?

Q. Let both p and k be prime numbers such that (p² + k) is also a prime number less than 30. What is the number of possible values of k?

Q. There are n sets of numbers each having only three positive integers with LCM equal to 1001 and HCF equal to 1. What is the value of n?

Q. Consider the sequence AB_CC_A_BCCC_BBC_C that follows a certain pattern. Which one of the following completes the sequence?

Q. What is the maximum value of n such that 7 × 343 × 385 × 1000 × 2401 × 77777 is divisible by 35ⁿ?

Q. What is X in the sequence 24, X, 12, 18, 36, 90?

Q. P and Q walk along a circular track. They start at 5:00 a.m. from the same point in opposite directions. P walks at an average speed of 5 rounds per hour and Q walks at an average speed of 3 rounds per hour. How many times will they cross each other between 5:20 a.m. and 7:00 a.m.?

Q. If P = +, Q = -, R = ×, S = ÷, then insert the proper notations between the successive numbers in the equation 60_15_3_20_4 = 20:

Q. A tram overtakes 2 persons X and Y walking at an average speed of 3 km/hr and 4 km/hr in the same direction and completely passes them in 8 seconds and 9 seconds respectively. What is the length of the tram?

Q. If N² = 12345678987654321, then how many digits does the number N have?

Q. A set (X) of 20 pipes can fill 70% of a tank in 14 minutes. Another set (Y) of 10 pipes fills 3/8th of the tank in 6 minutes. A third set (Z) of 16 pipes can empty half of the tank in 20 minutes. If half of the pipes of set X are closed and only half of the pipes of set Y are open, and all pipes of the set (Z) are open, then how long will it take to fill 50% of the tank?

Q. If n is a natural number, then what is the number of distinct remainders of (1ⁿ + 2ⁿ) when divided by 4?

Q. Let P = QQQ be a 3-digit number. What is the HCF of P and 481?

Q. What is the 489th digit in the number 123456789101112…?

Q. A mobile phone has been stolen. There are 3 suspects P, Q and R. They were questioned knowing that only one of them is guilty. Their responses are as follows:

Q. Three teams P, Q, R participated in a tournament in which the teams play with one another exactly once. A win fetches a team 2 points and a draw 1 point. A team gets no point for a loss. Each team scored exactly one goal in the tournament. The team P got 3 points, Q got 2 points and R got 1 point. Which of the following statements is/are correct?

Q. P is the brother of Q and R. S is R’s mother. T is P’s father. How many of the following statements are definitely true?

Q. If NO is coded as 210, NOT is coded as 4200 and NOTE is coded as 21000, then how is NOTES coded?

Q. If FRANCE is coded as 654321 and GERMANY is coded as 9158437, then how is YEMEN coded?

Q. The 5-digit number PQRST (all distinct digits) is such that T ≠ 0. P is thrice T. S is greater than Q by 4, while Q is greater than R by 3. How many such 5-digit numbers are possible?

Q. X can complete one-third of a certain work in 6 days, Y can complete one-third of the same work in 8 days and Z can complete three-fourth of the same work in 12 days. All of them work together for n days and then X and Z quit and Y alone finishes the remaining work in 8 2/3 days. What is n equal to?

Q. What is X in the sequence 1, 3, 6, 11, 18, X, 42?

Q. There are 7 places A, B, C, D, E, F and G in a city connected by various roads AB, AC, CD, DE, BF, EG and FG. A is 6 km south of B. A is 10 km west of C. D is 5 km east of E. C is 6 km north of D. F is 9 km west of B. F is 12 km north of G. A person travels from D to F through these roads. What is the distance covered by the person?

Q. In a certain code if 64 is written as 343 and 216 is written as 729, then how is 512 written in that code?

Q. What is the remainder when 9³ + 9⁴ + 9⁵ + 9⁶ + … + 9¹⁰⁰ is divided by 6?

Q. Question: What is the smallest 1-digit number having exactly 4 distinct factors?

Q. Question: Let P, Q, R, S be distinct non-zero digits. If PP × PQ = RRSS, where P ≤ 3 and Q ≤ 4, then what is Q equal to?

Q. Question: How is Q related to P? Statement I: P has two sisters, R and S.

Q. Question: In a football match, team P playing against Q was behind by 3 goals with 10 minutes remaining. Does team P win the match?

Q. Question: Is (p + q)² – 4pq, where p, q are natural numbers, positive?

Q. In a T20 cricket match, three players X, Y and Z scored a total of 37 runs. The ratio of number of runs scored by X to the number of runs scored by Y is equal to ratio of number of runs scored by Y to number of runs scored by Z.

Q. Let p + q = 10, where p, q are integers. Value-I = Maximum value of p × q when p, q are positive integers.

Q. Consider a set of 11 numbers: Value-I = Minimum value of the average of the numbers of the set when they are consecutive integers ≥ -5.

Q. The average of three numbers p, q and r is k. p is as much more than the average as q is less than the average. What is the value of r?

Q. Let x be a real number between 0 and 1. Which of the following statements is/are correct? I. x² > x³. II. x > √x.

Q. The difference between any two natural numbers is 10. What can be said about the natural numbers which are divisible by 5 and lie between these two numbers?

Q. There exists a natural number which when increased by 50% can have its number of factors unchanged.

Paragraph: Maintaining an ecosystem just to conserve biodiversity will affect its commercial potential as well as the livelihoods dependent on the ecosystem.

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