UPSC Prelims 2022 · CSAT
Question 57: Basic Numeracy
24 men and 12 women can do a piece of work in 30 days. In how many days can 12 men and 24 women do the same piece of work?
AnswerUPSC’s answer is (d).
The 30 days fix only one combination of the two efficiencies. Let a man do m and a woman do w units of work per day, so the job is 30 × (24m + 12w). The second group does 12m + 24w per day, which depends on the ratio of m to w. If m = w, the time is 30 days; if men are faster it takes more than 30 days; if women are faster it takes fewer. The data is inadequate.
How you could have got this
No shortcut here: in a “how many” question, ruling out options doesn’t help. Every statement has to be judged.
Which options go is worked out from UPSC’s key and the options, not by a model.
Why each option is right or wrong
- (a) Wrong: 30 days only if men and women work equally fast.
- (b) Wrong: more than 30 days only if men are faster.
- (c) Wrong: it rules out exactly 30 days, which occurs when men and women work equally fast.
- (d) Correct: the answer depends on relative efficiency, which is not given.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2022, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.