UPSC Prelims 2002 · General Studies

Question 63: Basic Numeracy

The age of a man is three times the sum of the ages of his two sons. Five years hence, his age will be double the sum of the ages of his sons. The father’s present age is

a40 years

b45 years

c50 years

d55 years

AnswerThe answer is (b).

Let the sons' ages add up to S; the father is then 3S. Five years later the father is 3S + 5 and the two sons together are S + 10, so 3S + 5 = 2(S + 10). Hence S = 15 and the father is 45 years old. Check: after five years he is 50 and the sons total 25, and 50 = 2 x 25.

Why each option is right or wrong

(a) 40 gives S of about 13.3 and fails the second condition.
(b) Right: 45 = 3 x 15, and 50 = 2 x 25.
(c) 50 gives S of about 16.7 and fails the second condition.
(d) 55 gives S of about 18.3 and fails the second condition.

Explanation: written by UPSC Grade, not by UPSC.

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Source: UPSC, Civil Services (Preliminary) Examination 2002, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.