Two pipes A and B can separately fill a tank in 12 minutes and 16 minutes respectively. Both the pipes are opened together but 4 minutes after the start the pipe A is turned off. How much time will it take to fill the tank? Choose the correct choice:
A) 5min
B) 7min
C) 8min
D) 9min
E) 10min
4/12 + x/16 = 1   x = 10   ANSW10minR:10min
<result>E</result>
Two pipes A and B can separately fill a tank in 12 minutes and 16 minutes respectively. Both the pipes are opened together but 4 minutes after the start the pipe A is turned off. How much time will it take to fill the tank?