2017 CSAT, all questions

UPSC Prelims 2017 · CSAT

Question 50: Logical Reasoning and Mental Ability

Examine the following statements :

  1. 1.All colours are pleasant.
  2. 2.Some colours are pleasant.
  3. 3.No colour is pleasant.
  4. 4.Some colours are not pleasant.

Given that statement 4 is true, what can be definitely concluded?

a1 and 2 are true.
b3 is true.
c2 is false.
d1 is false.

AnswerUPSC’s answer is (d).

Statement 4 says some colours are not pleasant. That directly contradicts statement 1, which says all colours are pleasant, so 1 is definitely false. Statements 2 and 3 are not settled: if some colours are not pleasant, the rest may or may not be. So the only definite conclusion is that statement 1 is false. In such sets, a particular negative always makes the matching universal affirmative false.

  • 1. Definitely false: it contradicts statement 4.
  • 2. Cannot be decided: some colours may be pleasant while others are not.
  • 3. Cannot be decided: statement 4 does not say whether any colour is pleasant.
  • 4. Given as true.
Why each option is right or wrong
  • (a) 1 is false, so 1 and 2 cannot both be true.
  • (b) 3 is not settled; some colours could still be pleasant.
  • (c) 2 may be true (some pleasant, some not), so it cannot be called false.
  • (d) Correct: 1 contradicts statement 4.

Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.

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Source: UPSC, Civil Services (Preliminary) Examination 2017, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.