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 answer: A) 8 B) 10 C) 12 D) 14 E) 15
4/12 + x/15 = 1   x = 10 min   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?