UPSC Prelims 2016 · CSAT
Question 7: Logical Reasoning and Mental Ability
A ate grapes and pineapple; B ate grapes and oranges; C ate oranges, pineapple and apple; D ate grapes, apple and pineapple. After taking fruits, B and C fell sick. In the light of the above facts, it can be said that the cause of sickness was :
AnswerUPSC’s answer is (d).
Work by elimination: find what the two who fell sick shared. B ate grapes and oranges; C ate oranges, pineapple and apple. Only oranges are common to both. Grapes were eaten by A and D, who stayed well; so were pineapple (A and D) and apple (D). So the cause was oranges. Method to remember: a cause must be present in every case where the effect occurs and absent where it does not.
Why each option is right or wrong
- (a) Apple was eaten by D, who stayed well.
- (b) Pineapple was eaten by A and D, both healthy.
- (c) Grapes were eaten by A and D, both healthy.
- (d) Right: oranges are the only fruit eaten by both sick persons and by neither healthy one.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2016, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.