Two pipes A and B can fill a tank in 15 min and 24 min respectively. Both the pipes are opened together but after 4 min, pipe A is turned off. What is the total time required to fill the tank?
Choose the correct choice from the following answers:
A) 14 min 19 sec
B) 14 min 42 sec
C) 14 min 20 sec
D) 16 min 48 sec
E) 14 min 10 sec
:   Part filled in 4 minutes = 4(1/15 + 1/20) = 7/15   Remaining part = 1 - 7/15 = 8/15   Part filled by B in 1 minute = 1/24   1/24 : 8/15 :: 1 ; x   x = 8/15 * 1 * 24 = 12 4/5 min = 12 min 48 sec.   The tank will be full in (4 min. + 12 min. 48 sec) = 16 min 48 sec.Answer: 16 min 48 sec
<result>D</result>
Two pipes A and B can fill a tank in 15 min and 24 min respectively. Both the pipes are opened together but after 4 min, pipe A is turned off. What is the total time required to fill the tank?