2024 CSAT, all questions
UPSC Prelims 2024 · CSAT
Question 80: Logical Reasoning and Mental Ability
In some code, letters P, Q, R, S, T represent numbers 4, 5, 10, 12, 15. It is not known which letter represents which number. If Q − S = 2S and T = R + S + 3, then what is the value of P + R − T ?
a1
b2
c3
dCannot be determined due to insufficient data
AnswerUPSC’s answer is (b).
Q − S = 2S means Q = 3S, so (S, Q) is (4, 12) or (5, 15). Then T = R + S + 3. If S = 4, then T = R + 7 from the remaining 5, 10, 15 has no fit. If S = 5 and Q = 15, then T = R + 8 from the remaining 4, 10, 12 gives R = 4 and T = 12, so P = 10. Then P + R − T = 10 + 4 − 12 = 2.
Why each option is right or wrong
- (a) Wrong. The only consistent assignment gives 2, not 1.
- (b) Right. P = 10, R = 4, T = 12 gives 2.
- (c) Wrong. The only consistent assignment gives 2, not 3.
- (d) Wrong. The assignment is unique, so the value is determined.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2024, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.