Two pipes can fill a tank in 24 min and 32 min respectively. If both the pipes are opened simultaneously, after how much time B should be closed so that the tank is full in 18 min ?	Choose the correct choice from the following
A) 4 min  B) 6 min  C) 9 min  D) 8 min  E) 12 min
Pipe A will run for 18 minutes   Sp pipe A will do = 18/24 = 3/4 portion of the work   left work is 1/ 4   Just assume that what will be 1/4 if multiplied with 1/32 (B's rate )   Only 8 will make it 1/4   So after 8 minutes B should be stopped   Answer : 8 min
<result>D</result>
Two pipes can fill a tank in 24 min and 32 min respectively. If both the pipes are opened simultaneously, after how much time B should be closed so that the tank is full in 18 min ?