Question 73

The ratios of efficiencies of A and B of doing a certain work is 5 : 8. Working together they can complete the work in 20 days, A alone will complete 25% of that work in:

Solution

Let total work to be done be L.C.M. (13,20) = 260 units

Let work done by A in 1 day = $$5x units$$ and by B = $$8x$$ units

=> Total work done in 1 day by A and B = $$(5x+8x)=13x$$ units

According to ques, => $$13x\times20=260$$

=> $$x=\frac{260}{260}=1$$

$$\therefore$$ A alone will complete 25% of work in = $$(\frac{25}{100}\times260)\div5$$

= $$\frac{65}{5}=13$$ days

=> Ans - (D)

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