UPSC Prelims 2012 · CSAT
Question 40: Logical Reasoning and Mental Ability
Only six roads A, B, C, P, Q and R connect a military camp to the rest of the country. Only one out of A, P and R is open at any one time. If B is closed, so is Q. Only one of A and B is open during storms. P is closed during floods. In this context, which one of the following statements is correct ?
AnswerUPSC’s answer is (b).
During storms exactly one of A and B is open, so at least one road is open: option (b). The other options cannot be established. Under normal conditions only one of A, P and R is open, but B, C and Q are not otherwise fixed, so the number open is not necessarily three. In floods P is closed, but again the count is not fixed at three. And since storms always leave A or B open, all roads are not closed in calamities.
Why each option is right or wrong
- (a) Wrong. Only one of A, P, R is open, but B, C and Q can vary, so the count is not fixed at three.
- (b) Right. Exactly one of A and B is open during storms, so at least one road is open.
- (c) Wrong. In floods P is closed, but the number open is not fixed at three.
- (d) Wrong. Storms always leave one of A or B open.
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.