Two pipes A and B can separately fill a tank in 2 minutes and 15 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 from the following:
A) 33  B) 10  C) 99  D) 73  E) 23
4/12 + x/15 = 1   x = 10   Answer: 10
<result>B</result>
Two pipes A and B can separately fill a tank in 2 minutes and 15 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?