If A, B, and C can do a piece of work in 15, 30, and 60 days respectively. In how many days together they will do the same work?

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RRB NTPC Exam 20 Jan 2021 click here to view all questions

If A, B, and C can do a piece of work in 15, 30, and 60 days respectively. In how many days together they will do the same work?

A10 days

B12 days

C60/11 days

D60/7 days

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correct answer is: option d) [60/7 days] Explanation: Let A, B, and C complete the work in 15, 30, and 60 days respectively. Work done by A in 1 day = $\frac{1}{15}$ Work done by B in 1 day = $\frac{1}{30}$ Work done by C in 1 day = $\frac{1}{60}$ Work done by A, B, and C together in 1 day = $\frac{1}{15}+\frac{1}{30}+\frac{1}{60}$ = $\frac{4+2+1}{60}$ = $\frac{7}{60}$ Therefore, the number of days required for A, B, and C to complete the work together = $\frac{60}{7}$ days. Option a: 10 days is incorrect because the combined work rate is faster than this. Option b: 12 days is incorrect because the combined work rate is faster than this. Option c: 60/11 days is incorrect because the sum of the individual work rates is not 11/60. Akhilesh ? answered Apr 7 '25 at 21:47

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