Question
C can do a piece of work in 20 days, and D can do the
same work in 25 days. They start working together, but after 8 days, C leaves. In how many more days will D finish the remaining work?Solution
Work done by C in 1 day = 1/20 Work done by D in 1 day = 1/25 Work done by C and D together in 1 day = (1/20) + (1/25) Taking LCM of 20 and 25 = 100, Work done together = (5/100) + (4/100) = 9/100 Work done in 8 days = 8 × (9/100) = 72/100 = 18/25 Remaining work = 1 - 18/25 = 7/25 D’s work rate = 1/25     Time taken by D to finish = (7/25) ÷ (1/25) = 7 days. Correct Option: c) 7 days
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