Question 59

C alone can complete a work in 20 days and D alone can complete the same workin 30 days. In how many days C and D together can complete the same work?

Solution

Let total work = L.C.M. (20,30) = 60 units

C can complete it in 20 days, => C's efficiency = $$\frac{60}{20}=3$$ units/day

Similarly, D's efficiency = $$\frac{60}{30}=2$$ units/day

=> $$(C+D)'s$$ 1 day's work = $$(3+2)=5$$ units

$$\therefore$$ Time taken by C and D together = $$\frac{60}{5}=12$$ days

=> Ans - (B)

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