Question

pipe A can fill a cistern in 6 hours and pipe B can fill it in 8 hours both the pipes are opened and after two hours, pipe A is closed. how much time will be take to fill the remaining part of the tank?

Answer 1

The rate of filling of pipe A in 1 hour = 1/6.

The rate of filling of pipe B in 1 hour = 1/8.

Rate of filling when both are opened together in 1 hour = 1/6 + 1/8

                                                                                             = 7/24.


Given that both the pipes are opened after 2 hours = 2 * (7/24)

                                                                                       = 7/12.

Leftover portion = 1 - 7/12

                             = 5/12


Therefore 5/12 of the tank is filled by B, which fills 1/8 tank in 1 hour.

So, it takes 3 1/3 hours to fill 5/12 of the tank.


Therefore the required time = 3 1/3 hours.



Hope this helps!

Answer 2

Hi

Please see the attached file!

Thanks