UPSC Prelims 2010 · General Studies
Question 131: Logical Reasoning and Mental Ability
Examine the following statements :
- 1.All colours are pleasant.
- 2.Some colours are pleasant.
- 3.No colour is pleasant.
- 4.Some colours are not pleasant.
Given that the statement 4 is true, what can be definitely concluded ?
AnswerThe answer is (b).
Statement 4, 'Some colours are not pleasant', is given as true. If some colours are not pleasant, it cannot be that all colours are pleasant, so statement 1 is definitely false. Statements 2 and 3 are not settled by statement 4: 'some colours are pleasant' may be true or false, and 'no colour is pleasant' may also be true or false. Only the falsity of statement 1 can be concluded. Remember: 'some are not' contradicts 'all are' and leaves 'some are' and 'none are' open.
Why each option is right or wrong
- (a) Statement 1 is false, so both cannot be true.
- (b) Right: statement 4 contradicts statement 1, so 1 is false.
- (c) Statement 2 may be true, so it cannot be concluded false.
- (d) Statement 3 may be true or false; it is not forced.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2010, General Studies, Series A. The paper on upsc.gov.in.