Two pipes A and B can fill a cistern in 37 1/2minutes and 45 minutes respectively. Both pipes are opened. The cistern will be filled in just half an hour, if pipe B is turned off after  Options
A) 5 min	B) 9 min	C) 10 min	D) 15 min	E) 17 min
Explanation:   Part filled by pipe A in 1 minute = 2 7/5   Part filled by pipe B in 1 minute =1 4/5   Suppose pipe B is closed after x minutes. Then,   2 7/5 × 30 +1 4/5 × x =1   4/5 +x/45 =1   x=9   Answer: Option 9 min
<result>B</result>
Two pipes A and B can fill a cistern in 37 1/2minutes and 45 minutes respectively. Both pipes are opened. The cistern will be filled in just half an hour, if pipe B is turned off after