Question

A cistern has two inlets A and B which can fill it in 12 minutes and 15 minutes respectively. An outlet C can empty the full cistern in 10 minutes. If all the 3 pipes are opened together in the empty cistern, in how many hours will the cistern be completely full?​

Answer 1

Solution-

Time taken by pipe A to fill the tank = 12 minutes

Time tekken bi pipe B to feel the time = 15 minutes

Time taken by pipe C to empty the tank = 10 minutes

In one minute, pipe A fills 1/12 of the tank.

In one minute, pipe B fills 1/15 of the tank.

In one minute, pipe C empties 1/10 of the tank.

Thus, in one minute, ( 1/12+1/15-1/10) part all the time is filled.

Hence, the tank will be full in 20 minutes.