UPSC Prelims 2020 · CSAT
Question 55: Basic Numeracy
In adult population of a city, 40% men and 30% women are married. What is the percentage of married adult population if no man marries more than one woman and no woman marries more than one man; and there are no widows and widowers?
AnswerUPSC’s answer is (c).
Marriages are one man to one woman, so the number of married men equals the number of married women. Let men = M and women = W. Then 0.4M = 0.3W, giving W = 4M/3. Married people = 2 × 0.4M = 0.8M, out of a total of M + 4M/3 = 7M/3. Percentage = 0.8M ÷ (7M/3) × 100 = 240/7 = 34 2/7%.
Why each option is right or wrong
- (a) 33 1/7% does not match 240/7.
- (b) 34% is close but not exact; 240/7 is 34 2/7.
- (c) Right: 240/7 = 34 2/7%.
- (d) 35% is the plain average of 40 and 30, which ignores the unequal numbers of men and women.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2020, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.