UPSC Prelims 2021 · CSAT
Question 15: Logical Reasoning and Mental Ability
A Statement followed by Conclusion-I and Conclusion-II is given below. You have to take the Statement to be true even if it seems to be at variance from the commonly known facts. Read all Conclusions and then decide which of the given Conclusion(s) logically follows/follow from the Statement, disregarding the commonly known facts.
- StatementSome cats are almirahs. Some almirahs are chairs. All chairs are tables.
- Conclusion-ICertainly some almirahs are tables.
- Conclusion-IISome cats may not be chairs.
Which one of the following is correct ?
AnswerUPSC’s answer is (c).
Sets: some cats are almirahs; some almirahs are chairs; every chair is a table. I: the almirahs that are chairs are also tables, because all chairs are tables, so some almirahs are certainly tables. II: the cats that are almirahs need not be the almirahs that are chairs, so it is possible that some cats are not chairs. A conclusion with 'may' needs only possibility, which is not ruled out. Both follow. Remember: a universal statement carries its property to any overlap with its subject, and 'may not' needs just one possible case.
- I. Some almirahs are chairs and all chairs are tables, so those almirahs are tables.
- II. Cats that are almirahs need not be chairs, so it is possible that some cats are not chairs.
Why each option is right or wrong
- (a) Conclusion I follows, but II also holds because it is possible that some cats are not chairs.
- (b) II follows, but so does I, via the almirahs that are chairs and hence tables.
- (c) Right: I through all chairs being tables; II because cats need not be chairs.
- (d) Fails: I is certain from the almirahs that are chairs, and II is possible.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2021, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.