2012 CSAT, all questions
UPSC Prelims 2012 · CSAT
Question 17: Logical Reasoning and Mental Ability
Examine the following statements :
- 1.Either A and B are of the same age or A is older than B.
- 2.Either C and D are of the same age or D is older than C.
- 3.B is older than C.
Which one of the following conclusions can be drawn from the above statements ?
aA is older than B
bB and D are of the same age
cD is older than C
dA is older than C
AnswerUPSC’s answer is (d).
Write the statements as rankings: A is at least as old as B (A >= B); D is at least as old as C (D >= C); B is older than C (B > C). Chaining A >= B > C gives A > C, so A is older than C. A may be the same age as B, nothing relates B to D, and D may be the same age as C, so the other conclusions are not forced. Remember: a chain containing one strict step gives a strict result.
Why each option is right or wrong
- (a) Wrong. A could be the same age as B.
- (b) Wrong. No statement relates B and D.
- (c) Wrong. D could be the same age as C.
- (d) Right. A is at least as old as B and B is older than C, so A is older than C.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2012, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.