Question 57

P alone can complete a work in 10 days and Q alone can complete the same work in 20 days. If P and Q work together, then in how many days the same work will be completed?

Solution

Let total work is L.C.M. (10,20) = 20 units

P alone can complete a work in 10 days, => P's efficiency = $$\frac{20}{10}=2$$ units/day

Similarly Q's efficiency = $$\frac{20}{20}=1$$ unit/day

Now, (P+Q)'s 1 day's work = $$2+1=3$$ units/day

$$\therefore$$ Days required by P and Q together to complete the work = $$\frac{20}{3}=6\frac{2}{3}$$ days

=> Ans - (B)

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