Two pipes A and B can fill a cistern in 16 and 24 minute respectively both fill pipes are opened together but 4

Two pipes A and B can fill a cistern in 16 and 24 minute respectively both fill pipes are opened together but 4 minutes before the cistern take to fill pipe B is closed. In how much time the cistern will get filled.

(a)          13 min

(b)          57/5min

(c)           11 1/5  min.

(d)          10 min

Sol:

In 4 min B can fill = 2 × 4 = 8 unit