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 choices.
A) 22 B) 10 C) 28 D) 27 E) 19
Explanation:   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?