Pipes And Cisterns Q6

6. A pipe can fill a tank in 5 hrs but because of a leak a the bottom it takes 1 hr extra. In what time can the leak alone empty the tank?

A.15 hrs                                           B.25 hrs

C.30 hrs                                           D.50 hrs

Answer:

Let the filling pipe be A.

A = 1 / 5.

But with the leak L,  A – L = 1 / 6   ( A-L because leak is outlet)

So, 1/L = 1 / 5 – 1/ 6 = 1/30 => Leak can empty the tank in 30 hrs.