UPSC Prelims 2020 · CSAT
Question 33: Logical Reasoning and Mental Ability
Two Statements are given followed by two Conclusions : Statements : All cats are dogs. All cats are black.
- Conclusion–IAll dogs are black.
- Conclusion–IISome dogs are not black.
Which of the above Conclusions logically follows/follow from the two given Statements, disregarding commonly known facts?
AnswerUPSC’s answer is (c).
All cats are dogs and all cats are black, so every cat is both a dog and black. Nothing is said about dogs that are not cats, so we cannot say all dogs are black (I). Equally, nothing says any dog is non-black, so II does not follow either. A valid conclusion would speak only of cats, or say that some dogs are black.
- I. Only cats are shown to be black; other dogs are undetermined.
- II. No dog is shown to be non-black.
Why each option is right or wrong
- (a) I would need every dog to be a cat.
- (b) II is not forced either: dogs that are not cats could be black.
- (c) Right: neither follows, since dogs outside the cats are undetermined.
- (d) I and II contradict each other, so both cannot follow.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2020, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.