UPSC Prelims 2010 · General Studies
Question 80: Logical Reasoning and Mental Ability
Half of the villagers of a certain village have their own houses. One-fifth of the villagers cultivate paddy. One-third of the villagers are literate. Four-fifth of the villagers are below twenty five. Then, which one of the following is certainly true ?
AnswerThe answer is (b).
One-third of the villagers are literate and four-fifths are under twenty-five. Together these fractions add up to 1/3 + 4/5 = 17/15, which is more than the whole village, so at least 2/15 of the villagers must be both literate and under twenty-five. Hence some villagers under twenty-five are literate. The other options claim exact relations that the data do not fix. Remember: when two groups add up to more than the whole, they must overlap.
Why each option is right or wrong
- (a) Half own houses but only a third are literate, so not all of them can be literate.
- (b) Right: the overlap between the literate and the under-twenty-five is forced.
- (c) No data link house ownership with paddy cultivation.
- (d) A fifth cultivate paddy and a third are literate; nothing fixes the overlap.
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.