Question 33

Mohan is thrice as efficient as Srinu and completes a work in 40 hours less than the time taken by Srinu. If both of them work together, the time (in hours) required to complete that work is

Solution

Let,Srinu takes x hour to complete work.

then Mohan takes x/3 hour to complete the work.

According to question,

$$x\ -40=\frac{x\ }{3}.$$

or,$$x\ -\frac{x\ }{3}=40.$$

or,$$\frac{2x\ }{3}=40.$$

or,$$x\ =60.$$

Then,they will do in 1 hour $$\ \frac{\ 1}{20}+\frac{1\ }{60}=\frac{3+1\ }{60}=\frac{4\ }{60}=\frac{1`\ }{15}$$ part.

So, they together will complete in 15 hour.

C is correct choice.

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