Question 15

Both X and Y together can complete a work in 12 days and Y alone can complete the same work in 30 days. In how many days will X alone complete the work?

Solution

Let the total work to be done = L.C.M. (12,30) = 60 units

Y alone can complete the same work in 30 days, => Y's efficiency = $$\frac{60}{30}=2$$ units/day

Similarly, (X+Y)'s 1 day's work = $$\frac{60}{12}=5$$ units/day

=> X's efficiency = $$5-2=3$$ units/day

$$\therefore$$ Time taken by X to complete the work alone = $$\frac{60}{3}=20$$ days

=> Ans - (B)

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