2023 CSAT, all questions

UPSC Prelims 2023 · CSAT

Question 24: Logical Reasoning and Mental Ability

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

a6
b8
c13
d15

AnswerUPSC’s answer is (a).

Find the rule: add the three numbers, 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. All three examples match. For 23, 4, 15: the sum is 42, and 4 + 2 = 6.

Why each option is right or wrong
  • (a) Right: 23 + 4 + 15 = 42, and 4 + 2 = 6.
  • (b) Wrong: 8 is the result for the first set, not this one.
  • (c) Wrong: 13 is the result for the third set.
  • (d) Wrong: 15 comes from adding all the digits without first adding the numbers.

Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.

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Source: UPSC, Civil Services (Preliminary) Examination 2023, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.