UPSC Prelims 2015 · CSAT
Question 78: Logical Reasoning and Mental Ability
A society consists of only two types of people — fighters and cowards. Two cowards are always friends. A fighter and a coward are always enemies. Fighters are indifferent to one another. If A and B are enemies, C and D are friends, E and F are indifferent to each other, A and E are not enemies, while B and F are enemies. Which of the following statements is correct ?
AnswerUPSC’s answer is (b).
Friends are only two cowards; fighters are indifferent to each other; a fighter and a coward are enemies. A and B are enemies, so one is a fighter and the other a coward. C and D are friends, so both are cowards. E and F are indifferent, so both are fighters. A and E are not enemies and E is a fighter, so A cannot be a coward: A is a fighter and B a coward. B and F are enemies, a coward and a fighter, which is consistent. So A, E and F are fighters.
Why each option is right or wrong
- (a) Wrong: F is a fighter, so B, C and F are not all cowards.
- (b) Right: A, E and F are all fighters.
- (c) Wrong: B is a coward and E a fighter.
- (d) Wrong: A and F are both fighters.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2015, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.