2015 CSAT, all questions
UPSC Prelims 2015 · CSAT
Question 16: Basic Numeracy
A father is nine times as old as his son and the mother is eight times as old as the son. The sum of the father’s and the mother’s age is 51 years. What is the age of the son ?
a7 years
b5 years
c4 years
d3 years
AnswerUPSC’s answer is (d).
Let the son be x years. The father is 9x and the mother 8x, so their sum is 17x = 51. Dividing, x = 51 ÷ 17 = 3 years. Check: father 27 plus mother 24 gives 51, as stated. In such problems add the multiples first and divide the total by that sum.
Why each option is right or wrong
- (a) Wrong: 7 gives 17 × 7 = 119, not 51.
- (b) Wrong: 5 gives 85, not 51.
- (c) Wrong: 4 gives 68, not 51.
- (d) Right: 17 × 3 = 51.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2015, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.