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UPSC prelims CSAT reasoning: previous year questionsUPSC प्रीलिम्स CSAT तर्कशक्ति: पिछले वर्षों के प्रश्न

43 questions from the prelims papers of 2018 to 2025, newest first. Read the question, try it, then open the answer: it comes from the official UPSC answer key, with a short explanation.2018 से 2025 तक के प्रीलिम्स पेपरों से 43 प्रश्न, नए पहले। प्रश्न पढ़िए, हल कीजिए, फिर उत्तर खोलिए: वह आधिकारिक UPSC उत्तर-कुंजी से है, साथ में छोटी व्याख्या।

Questionsप्रश्न

  1. UPSC 2025 CSAT, question 8प्रश्न 8

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

    1. July, May
    2. July, April
    3. June, May
    4. June, April
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (b) July, April

    Count back through the months by 0, 1, 2, 3, ... each time (wrapping round the year). January back 0 is January; back 1 is December; back 2 is October; back 3 is July (X); back 4 is March; back 5 is October; back 6 is April (Y); back 7 is September. So X = July and Y = April.

  2. UPSC 2025 CSAT, question 15प्रश्न 15

    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? I. The minimum number of cuts is 9. II. The number of smaller pieces which are not painted on any face is 6. Select the correct answer using the code given below:

    1. I only
    2. II only
    3. Both I and II
    4. Neither I nor II
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (c) Both I and II

    To get 60 pieces with the fewest cuts, split the three directions as evenly as possible: 60 = 3 x 4 x 5, which needs (3 - 1) + (4 - 1) + (5 - 1) = 2 + 3 + 4 = 9 cuts. So I is correct. The unpainted pieces form the inner block of (3 - 2) x (4 - 2) x (5 - 2) = 1 x 2 x 3 = 6 pieces, so II is also correct.

  3. UPSC 2025 CSAT, question 16प्रश्न 16

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

    1. 70
    2. 66
    3. 65
    4. 64
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (c) 65

    The operation gives the hypotenuse: a * b = square root of (a^2 + b^2). Check: 49 + 576 = 625, root 25; 144 + 256 = 400, root 20. So 16 * 63 = square root of (256 + 3969) = square root of 4225 = 65.

  4. UPSC 2025 CSAT, question 19प्रश्न 19

    Consider the following statements: I. If A ≤ B > C < D > E > F ≥ G = H; then B is always greater than E. II. If P > Q = R ≥ S = T ≤ U = V > W; then S is always less than V. Which of the statements given above is/are correct?

    1. I only
    2. II only
    3. Both I and II
    4. Neither I nor II
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (d) Neither I nor II

    I: B > C and C < D > E. Because the signs between B and E change direction at C, no definite relation between B and E can be fixed, so I is not always true. II: S = T ≤ U = V gives S ≤ V, so S could be equal to V; 'always less than' is not guaranteed. Neither statement is correct.

  5. UPSC 2025 CSAT, question 30प्रश्न 30

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

    1. B, C, B, C, A
    2. A, C, B, C, A
    3. B, C, B, A, C
    4. C, B, B, A, C
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (c) B, C, B, A, C

    Filling the blanks with B, C, B, A, C gives ABBCCC ABBCCC ABBCCC, the block ABBCCC (one A, two B, three C) repeated three times. No other option keeps this repeating pattern.

  6. UPSC 2025 CSAT, question 36प्रश्न 36

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

    1. 18
    2. 12
    3. 9
    4. 6
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (b) 12

    Each term is the previous one multiplied by 0.5, 1, 1.5, 2, 2.5 in turn: 24 x 0.5 = 12, 12 x 1 = 12, 12 x 1.5 = 18, 18 x 2 = 36, 36 x 2.5 = 90. So X = 12.

  7. UPSC 2025 CSAT, question 49प्रश्न 49

    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: P: I did not steal. Q stole it. Q: R did not steal. I did not steal. R: I did not steal. I do not know who did it. Who stole the mobile phone?

    1. P
    2. Q
    3. R
    4. Cannot be concluded
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (d) Cannot be concluded

    We are told only that one person is guilty; nothing is said about who tells the truth or how many statements are true. Each case is possible: if P stole it, P lied and Q and R can be truthful; if Q stole it, P is truthful and Q lied; if R stole it, P and Q lied. Without a condition on truth-telling, none of these can be ruled out, so the thief cannot be concluded.

  8. UPSC 2025 CSAT, question 50प्रश्न 50

    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? I. The result of the match between P and Q is a draw with the score 0 - 0. II. The number of goals scored by R against Q is 1. Which of the statements given above is/are correct?

    1. I only
    2. II only
    3. Both I and II
    4. Neither I nor II
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (c) Both I and II

    P's 3 points must be a win and a draw, and R's 1 point a draw and a loss. If Q had a win and a loss, Q could not beat P (P has no loss), so Q would beat R and lose to P, and P would draw with R; then P's one goal is used against Q, so P-R is 0-0 and Q's goal is against R, leaving R with no goal, which is impossible. So Q drew both matches, and P beat R. P's only goal came against R (1-0), so P-Q was 0-0. R scored nothing against P, so R's goal came against Q, and Q's goal also came against R: Q-R was 1-1. Both I and II are correct.

  9. UPSC 2025 CSAT, question 55प्रश्न 55

    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? I. S and T are a couple. II. Q is T's son. III. T is Q's father. IV. S is P's mother. V. R is T's daughter. VI. P is S's son. Select the correct answer using the code given below:

    1. Only two
    2. Only three
    3. Only four
    4. Only five
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (c) Only four

    P, Q and R are siblings, so they share the parents S (mother) and T (father). Hence S and T are a couple (I), T is Q's father (III), S is P's mother (IV), and P, being a brother, is S's son (VI). The genders of Q and R are not given, so 'Q is T's son' (II) and 'R is T's daughter' (V) are not definitely true. Four statements are definitely true.

  10. UPSC 2025 CSAT, question 56प्रश्न 56

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

    1. 399000
    2. 420000
    3. 440000
    4. 630000
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (a) 399000

    The code is the product of the alphabet positions of the letters: N = 14, O = 15, so NO = 14 x 15 = 210; NOT = 210 x 20 (T) = 4200; NOTE = 4200 x 5 (E) = 21000. NOTES = 21000 x 19 (S) = 399000.

  11. UPSC 2025 CSAT, question 57प्रश्न 57

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

    1. 54321
    2. 81913
    3. 71913
    4. 71813
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (d) 71813

    Each letter keeps a fixed digit. From FRANCE: F = 6, R = 5, A = 4, N = 3, C = 2, E = 1. From GERMANY: G = 9, E = 1, R = 5, M = 8, A = 4, N = 3, Y = 7. So YEMEN = Y E M E N = 7 1 8 1 3 = 71813.

  12. UPSC 2025 CSAT, question 60प्रश्न 60

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

    1. 26
    2. 27
    3. 29
    4. 30
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (c) 29

    The differences are consecutive prime numbers: 1 + 2 = 3, 3 + 3 = 6, 6 + 5 = 11, 11 + 7 = 18, 18 + 11 = 29, 29 + 13 = 42. So X = 29.

  13. UPSC 2025 CSAT, question 66प्रश्न 66

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

    1. 1000
    2. 1331
    3. 1728
    4. 2197
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (b) 1331

    64 = 4^3 becomes 343 = 7^3, and 216 = 6^3 becomes 729 = 9^3: the cube root is increased by 3 and cubed again. 512 = 8^3, so it becomes 11^3 = 1331.

  14. UPSC 2025 CSAT, question 68प्रश्न 68

    A question is given followed by two Statements I and II. Consider the Question and the Statements and mark the correct option. Question: What is the smallest 1-digit number having exactly 4 distinct factors? Statement I: 2 is one of the factors. Statement II: 3 is one of the factors. Which one of the following is correct in respect of the above Question and the Statements?

    1. The Question can be answered by using one of the Statements alone, but cannot be answered using the other statement alone.
    2. The Question can be answered by using either Statement alone.
    3. The Question can be answered by using both the Statements together, but cannot be answered using either Statement alone.
    4. The Question can be answered even without using any of the Statements.
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (d) The Question can be answered even without using any of the Statements.

    Among 1 to 9, only 6 (1, 2, 3, 6) and 8 (1, 2, 4, 8) have exactly 4 factors. The smallest is 6. This is found directly, so the statements are not needed.

  15. UPSC 2025 CSAT, question 70प्रश्न 70

    A question is given followed by two Statements I and II. Consider the Question and the Statements and mark the correct option. Question: How is Q related to P? Statement I: P has two sisters, R and S. Statement II: R's father is the brother of Q. Which one of the following is correct in respect of the above Question and the Statements?

    1. The Question can be answered by using one of the Statements alone, but cannot be answered using the other statement alone.
    2. The Question can be answered by using either Statement alone.
    3. The Question can be answered by using both the Statements together, but cannot be answered using either Statement alone.
    4. The Question cannot be answered even using any of the Statements.
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (d) The Question cannot be answered even using any of the Statements.

    Statement I alone says nothing about Q, and Statement II alone says nothing about P. Together, R's father is also P's father, and Q is his sibling. But Q's gender is not known, so Q could be P's paternal uncle or paternal aunt. The exact relation cannot be fixed even with both statements.

  16. UPSC 2025 CSAT, question 73प्रश्न 73

    A question is given followed by two Statements I and II. Consider the Question and the Statements and mark the correct option. 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? Statement I: Team P scored 4 goals in the last 10 minutes. Statement II: Team Q scored a total of 4 goals in the match. Which one of the following is correct in respect of the above Question and the Statements?

    1. The Question can be answered by using one of the Statements alone, but cannot be answered using the other statement alone.
    2. The Question can be answered by using either Statement alone.
    3. The Question can be answered by using both the Statements together, but cannot be answered using either Statement alone.
    4. The Question cannot be answered even using any of the Statements.
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (d) The Question cannot be answered even using any of the Statements.

    Statement I alone fails because Q may also have scored in the last 10 minutes. Statement II alone says nothing about P. Together: if Q had g goals with 10 minutes left, P had g - 3, so g is at least 3, and P finishes with g + 1 against Q's 4. If g = 3 (P 0-3 down, Q scores no more), the match ends 4-4, a draw; if g = 4, P wins 5-4. Both cases fit the data, so the question cannot be answered.

  17. UPSC 2024 CSAT, question 5प्रश्न 5

    What is the least possible number of cuts required to cut a cube into 64 identical pieces?

    1. 8
    2. 9
    3. 12
    4. 16
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (b) 9

    64 identical small cubes means 4 x 4 x 4 pieces, so each edge must be divided into 4 parts. Dividing an edge into 4 parts needs 3 cuts, and this is needed along each of the three directions. Least number of cuts = 3 + 3 + 3 = 9.

  18. UPSC 2024 CSAT, question 24प्रश्न 24

    Consider the sequence A _ BCD _ BBCDABC _ DABC _ D that follows a certain pattern. Which one of the following completes the sequence?

    1. B, A, D, C
    2. B, A, C, D
    3. A, A, C, D
    4. A, A, D, C
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (c) A, A, C, D

    Filling A, A, C, D gives AABCD ABBCD ABCCD ABCDD. The series is made of blocks of ABCD in which one letter is doubled, moving one step each time: first A, then B, then C, then D. So the blanks are A, A, C, D.

  19. UPSC 2024 CSAT, question 37प्रश्न 37

    How many times the hour hand and the minute hand coincide in a clock between 10:00 a.m. and 2:00 p.m. (same day)?

    1. 3 times
    2. 4 times
    3. 5 times
    4. 6 times
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (a) 3 times

    The hands coincide once in every 12/11 hours, at about 10:54:33, 12:00 noon and 1:05:27 in this interval. The next coincidence after that is at about 2:10:54, which is after 2:00 p.m. So they coincide 3 times.

  20. UPSC 2024 CSAT, question 38प्रश्न 38

    The calendar for the year 2025 is same for

    1. 2029
    2. 2030
    3. 2031
    4. 2033
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (c) 2031

    2025 is an ordinary year beginning on a Wednesday. Each ordinary year moves the starting day by 1 and a leap year by 2: 2026 Thursday, 2027 Friday, 2028 Saturday (leap year), 2029 Monday, 2030 Tuesday, 2031 Wednesday. 2031 is also an ordinary year starting on Wednesday, so its calendar is the same as 2025.

  21. UPSC 2024 CSAT, question 40प्रश्न 40

    What is the angle between the minute hand and hour hand when the clock shows 4:25 hours?

    1. 12.5°
    2. 15°
    3. 17.5°
    4. 20°
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (c) 17.5°

    Angle = |30H - 5.5M| = |30 x 4 - 5.5 x 25| = |120 - 137.5| = 17.5°. (Minute hand at 25 x 6 = 150°, hour hand at 120 + 25 x 0.5 = 132.5°.)

  22. UPSC 2024 CSAT, question 56प्रश्न 56

    A person walks 100 m straight from his house, turns left and walks 100 m, again turns left and walks 300 m, then turns right and walks 100 m to reach his office. In which direction does he walk initially from his house if his office is exactly in the North-East direction?

    1. North-West
    2. West
    3. South
    4. South-West
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (c) South

    Test starting South: 100 m South, turn left so face East and walk 100 m, turn left so face North and walk 300 m, turn right so face East and walk 100 m. Net movement: 300 - 100 = 200 m North and 100 + 100 = 200 m East, so the office is exactly North-East. Hence he started walking South.

  23. UPSC 2024 CSAT, question 57प्रश्न 57

    A person walks 100 m Westward, then turns left and walks 100 m. He then takes 225° turn clockwise. In which direction is he walking now?

    1. South-West
    2. South-East
    3. North-West
    4. North-East
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (d) North-East

    Walking West, a left turn makes him face South. Turning clockwise from South: 90° gives West, 180° gives North, and a further 45° (total 225°) gives North-East.

  24. UPSC 2024 CSAT, question 58प्रश्न 58

    A Statement is given followed by two Conclusions numbered I and II. Consider the Statement and the Conclusions. Statement: India is the world's largest producer of milk. Conclusion-I: India is the world's largest exporter of milk. Conclusion-II: India does not import milk. Which one of the following is correct?

    1. Only Conclusion-I follows
    2. Only Conclusion-II follows
    3. Both Conclusion-I and Conclusion-II follow
    4. Neither Conclusion-I nor Conclusion-II follows
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (d) Neither Conclusion-I nor Conclusion-II follows

    Being the largest producer says nothing about trade. A large producer may consume most of its output at home, so it need not be the largest exporter (I does not follow), and it may still import some milk or milk products (II does not follow). Neither conclusion follows.

  25. UPSC 2024 CSAT, question 74प्रश्न 74

    A Main Statement is followed by four Statements labelled P, Q, R and S. Choose the ordered pair of the Statements where the first Statement implies the second, and the two Statements are logically consistent with the Main Statement. Main Statement: Pradeep becomes either a Director or a Producer. Statement P: Pradeep is a Director. Statement Q: Pradeep is a Producer. Statement R: Pradeep is not a Director. Statement S: Pradeep is not a Producer. Select the correct answer.

    1. SP only
    2. RQ only
    3. Both SP and RQ
    4. Neither SP nor RQ
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (c) Both SP and RQ

    For an 'either A or B' statement, denying one option forces the other. If Pradeep is not a Producer (S), he must be a Director (P), so SP is valid. If he is not a Director (R), he must be a Producer (Q), so RQ is valid. Both pairs are correct.

  26. UPSC 2024 CSAT, question 76प्रश्न 76

    If P means 'greater than (>)'; Q means 'less than (<)'; R means 'not greater than (≯)'; S means 'not less than (≮)' and T means 'equal to (=)', then consider the following statements: 1. If 2x(S)3y and 3x(T)4z, then 9y(P)8z. 2. If x(Q)2y and y(R)z, then x(R)z. Which of the statements given above is/are correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (d) Neither 1 nor 2

    Statement 1: 2x is not less than 3y, so 2x ≥ 3y; and 3x = 4z, so x = 4z/3 and 2x = 8z/3. Then 8z/3 ≥ 3y, that is 8z ≥ 9y, so 9y is not greater than 8z; the claim 9y > 8z is wrong. Statement 2: x < 2y and y ≤ z only give x < 2z. For example y = z = 10 and x = 15 satisfy both conditions but x > z, so 'x not greater than z' need not hold. Neither statement is correct.

  27. UPSC 2024 CSAT, question 77प्रश्न 77

    If in a certain code, 'ABCD' is written as 24 and 'EFGH' is written as 1680, then how is 'IJKL' written in that code?

    1. 11880
    2. 11240
    3. 7920
    4. 5940
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (a) 11880

    The code is the product of the alphabet positions of the letters. ABCD = 1 x 2 x 3 x 4 = 24 and EFGH = 5 x 6 x 7 x 8 = 1680. So IJKL = 9 x 10 x 11 x 12 = 11880.

  28. UPSC 2024 CSAT, question 78प्रश्न 78

    If in a certain code, 'POT' is written as ATOP and 'TRAP' is written as APART, then how is 'ARENA' written in that code?

    1. AARENA
    2. AANREA
    3. AANEAR
    4. AANERA
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (d) AANERA

    The word is written in reverse and the letter A is placed in front: POT reversed is TOP, giving ATOP; TRAP reversed is PART, giving APART. ARENA reversed is ANERA, so the code is AANERA.

  29. UPSC 2023 CSAT, question 6प्रश्न 6

    There are four letters and four envelopes and exactly one letter is to be put in exactly one envelope with the correct address. If the letters are randomly inserted into the envelopes, then consider the following statements: 1. It is possible that exactly one letter goes into an incorrect envelope. 2. There are only six ways in which only two letters can go into the correct envelopes. Which of the statements given above is/are correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (b) 2 only

    Statement 1: if three letters are in their correct envelopes, the only envelope left is the correct one for the fourth letter, so exactly one wrong letter is impossible. Statement 2: choose the two letters that go correctly in C(4, 2) = 6 ways; the other two must then swap envelopes, which can be done in exactly 1 way. So there are 6 ways, and only statement 2 is correct.

  30. UPSC 2023 CSAT, question 24प्रश्न 24

    If 7 ⊕ 9 ⊕ 10 = 8, 9 ⊕ 11 ⊕ 30 = 5, 11 ⊕ 17 ⊕ 21 = 13, what is the value of 23 ⊕ 4 ⊕ 15?

    1. 6
    2. 8
    3. 13
    4. 15
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (a) 6

    Add the three numbers and then add the digits of that sum. 7 + 9 + 10 = 26 and 2 + 6 = 8. 9 + 11 + 30 = 50 and 5 + 0 = 5. 11 + 17 + 21 = 49 and 4 + 9 = 13. So 23 + 4 + 15 = 42 and 4 + 2 = 6.

  31. UPSC 2023 CSAT, question 37प्रश्न 37

    If 'ZERO' is written as 'CHUR', then how is 'PLAYER' written?

    1. SOCAGT
    2. SODBGT
    3. SODBHT
    4. SODBHU
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (d) SODBHU

    Each letter moves 3 places forward: Z to C, E to H, R to U, O to R. Applying +3 to PLAYER: P to S, L to O, A to D, Y to B, E to H, R to U, giving SODBHU.

  32. UPSC 2023 CSAT, question 38प्रश्न 38

    Consider the following statements: 1. A is older than B. 2. C and D are of the same age. 3. E is the youngest. 4. F is younger than D. 5. F is older than A. How many statements given above are required to determine the oldest person/persons?

    1. Only two
    2. Only three
    3. Only four
    4. All five
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (d) All five

    Using all five: D > F (4), F > A (5), A > B (1), C = D (2) and E is the youngest (3). So C and D are the oldest. Every statement is needed: without 4 we cannot place D above F; without 5 we cannot place F above A; without 1 B could be older; without 2 we would not know C's age; and without 3 E could be the oldest. So all five are required.

  33. UPSC 2023 CSAT, question 39प्रश्न 39

    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?

    1. Statement-1, Statement-2 and Statement-3 are sufficient to answer the Question.
    2. Statement-1, Statement-3 and Statement-4 are sufficient to answer the Question.
    3. All four statements together are sufficient to answer the Question.
    4. All four statements are not sufficient to answer the Question.
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (c) All four statements together are sufficient to answer the Question.

    From 4, A and C are sisters, and from 2, D is the father of C, hence also of A. From 3, E is D's son, so E is the brother of A. From 1, B is A's spouse, so E is B's brother-in-law. Dropping any statement breaks the chain: without 2 or 4 we cannot connect D (and E) to A, without 3 we do not know E's link, and without 1 we cannot link B. So all four are needed.

  34. UPSC 2023 CSAT, question 40प्रश्न 40

    Choose the group which is different from the others:

    1. 17, 37, 47, 97
    2. 31, 41, 53, 67
    3. 71, 73, 79, 83
    4. 83, 89, 91, 97
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (d) 83, 89, 91, 97

    Groups (a), (b) and (c) contain only prime numbers. Group (d) contains 91, which is 7 x 13 and not prime, so (d) is the odd one out.

  35. UPSC 2023 CSAT, question 49प्रश्न 49

    If today is Sunday, then which day is it exactly on 10^10 th day?

    1. Wednesday
    2. Thursday
    3. Friday
    4. Saturday
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (a) Wednesday

    Count today as day 1, so the 10^10 th day comes 10^10 - 1 days after today. Since 10 leaves remainder 3 on division by 7, 10^10 leaves the same remainder as 3^10; 3^6 leaves 1, so 3^10 leaves the same as 3^4 = 81, which is 4. So 10^10 - 1 leaves remainder 3, and Sunday + 3 days = Wednesday. (If one instead counts 10^10 days after today, the result would be Thursday; the official key gives Wednesday, which follows the first reading.)

  36. UPSC 2023 CSAT, question 55प्रश्न 55

    What is the middle term of the sequence Z, Z, Y, Y, Y, X, X, X, X, W, W, W, W, W, . . ., A?

    1. H
    2. I
    3. J
    4. M
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (b) I

    Z appears 2 times, Y 3 times, X 4 times, and so on, so the n-th letter from Z appears n + 1 times and A (the 26th) appears 27 times. Total terms = 2 + 3 + ... + 27 = 377, so the middle term is the 189th. The first k letters use 2 + 3 + ... + (k + 1) = (k + 1)(k + 2)/2 - 1 terms; for k = 17 this is 170 and for k = 18 it is 189. So the 189th term is the last copy of the 18th letter counted from Z, which is the 9th letter of the alphabet, I.

  37. UPSC 2023 CSAT, question 56प्रश्न 56

    Question: Is p greater than q? Statement-1: p × q is greater than zero. Statement-2: p^2 is greater than q^2. Which one of the following is correct in respect of the above Question and the Statements?

    1. The Question can be answered by using one of the Statements alone, but cannot be answered using the other Statement alone.
    2. The Question can be answered by using either Statement alone.
    3. The Question can be answered by using both the Statements together, but cannot be answered using either Statement alone.
    4. The Question cannot be answered even by using both the Statements together.
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (d) The Question cannot be answered even by using both the Statements together.

    Statement 1 says p and q have the same sign; statement 2 says p is larger in size than q. Together they still do not decide the question: p = 3, q = 2 gives p > q, but p = -3, q = -2 also satisfies both statements and gives p < q. So the question cannot be answered even with both statements.

  38. UPSC 2023 CSAT, question 57प्रश्न 57

    Question: Is (p + q - r) greater than (p - q + r), where p, q and r are integers? Statement-1: (p - q) is positive. Statement-2: (p - r) is negative. Which one of the following is correct in respect of the above Question and the Statements?

    1. The Question can be answered by using one of the Statements alone, but cannot be answered using the other Statement alone.
    2. The Question can be answered by using either Statement alone.
    3. The Question can be answered by using both the Statements together, but cannot be answered using either Statement alone.
    4. The Question cannot be answered even by using both the Statements together.
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (c) The Question can be answered by using both the Statements together, but cannot be answered using either Statement alone.

    (p + q - r) - (p - q + r) = 2(q - r), so the question is really whether q > r. Statement 1 gives q < p and says nothing about r; statement 2 gives p < r and says nothing about q. Together, q < p < r, so q < r and the answer is a definite No. Both statements are needed together.

  39. UPSC 2023 CSAT, question 70प्रश्न 70

    Consider the following: I. A + B means A is neither smaller nor equal to B. II. A - B means A is not greater than B. III. A × B means A is not smaller than B. IV. A ÷ B means A is neither greater nor equal to B. V. A ± B means A is neither smaller nor greater than B. Statement: P × Q, P - T, T ÷ R, R ± S Conclusion-1: Q ± T Conclusion-2: S + Q Which one of the following is correct in respect of the above Statement and the Conclusions?

    1. Only Conclusion-1 follows from the Statement.
    2. Only Conclusion-2 follows from the Statement.
    3. Both Conclusion-1 and Conclusion-2 follow from the Statement.
    4. Neither Conclusion-1 nor Conclusion-2 follows from the Statement.
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (b) Only Conclusion-2 follows from the Statement.

    Decode the symbols: + means >, - means <=, × means >=, ÷ means < and ± means =. The statement becomes P >= Q, P <= T, T < R, R = S, which combine to Q <= P <= T < R = S. Conclusion 1 (Q = T) need not hold, since Q could be less than T. Conclusion 2 (S > Q) holds because S = R > T >= Q. Only Conclusion 2 follows.

  40. UPSC 2023 CSAT, question 75प्रश्न 75

    Consider the sequence ABC_ _ABC_DABBCD_ABCD that follows a certain pattern. Which one of the following completes the sequence?

    1. DACB
    2. CDAB
    3. DCCA
    4. DDCA
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (d) DDCA

    Filling the blanks with D, D, C, A gives ABCDDABCCDABBCDAABCD. Split into groups of four: ABCD, DABC, CDAB, BCDA, ABCD. Each group is the previous one with its last letter moved to the front, so the pattern holds and the answer is DDCA.

  41. UPSC 2023 CSAT, question 77प्रश्न 77

    Consider the following statements in respect of five candidates P, Q, R, S and T. Two statements are true and one statement is false. True Statement: One of P and Q was selected for the job. False Statement: At least one of R and S was selected for the job. True Statement: At most two of R, S and T were selected for the job. Which of the following conclusions can be drawn? 1. At least four were selected for the job. 2. S was selected for the job. Select the correct answer using the code given below:

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (d) Neither 1 nor 2

    Since 'at least one of R and S was selected' is false, neither R nor S was selected, so conclusion 2 is wrong. That leaves only P, Q and T as possible selections, so at most three people were selected and conclusion 1 is wrong too. Neither conclusion follows.

  42. UPSC 2023 CSAT, question 78प्रश्न 78

    Let P, Q, R, S and T be five statements such that: I. If P is true, then both Q and S are true. II. If R and S are true, then T is false. Which of the following can be concluded? 1. If T is true, then at least one of P and R must be false. 2. If Q is true, then P is true. Select the correct answer using the code given below:

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (a) 1 only

    Conclusion 1: suppose T is true and both P and R are true. From I, P makes S true; then R and S are both true, so by II, T is false, which is a contradiction. So if T is true, P and R cannot both be true, and conclusion 1 follows. Conclusion 2 reverses rule I: P being true forces Q to be true, but Q being true says nothing about P. So only 1 follows.

  43. UPSC 2023 CSAT, question 80प्रश्न 80

    The letters of the word "INCOMPREHENSIBILITIES" are arranged alphabetically in reverse order. How many positions of the letter/letters will remain unchanged?

    1. None
    2. One
    3. Two
    4. Three
    Answer and explanationउत्तर और व्याख्या

    Answer:उत्तर: (c) Two

    The word has 21 letters: I N C O M P R E H E N S I B I L I T I E S. In reverse alphabetical order they read T S S R P O N N M L I I I I I H E E E C B. Comparing position by position, the letters match only at position 13 (I) and position 15 (I). So two positions remain unchanged.

Questions and answer keys are published by the Union Public Service Commission (upsc.gov.in). Explanations are written by IndiaDigital; if one looks wrong, use the report link under it.प्रश्न और उत्तर-कुंजियाँ संघ लोक सेवा आयोग (upsc.gov.in) द्वारा प्रकाशित हैं। व्याख्याएँ IndiaDigital ने लिखी हैं; कोई गलत लगे तो उसके नीचे दिए लिंक से बताइए।

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