Two pipes A and B can fill a cistern in 37 1/2 minutes 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 Choose the most appropriate option: A) 5 min B) 9 min C) 10 min D) 15 min E) 16 min
Explanation:   Solution 1   Pipe A alone can fill the cistern in 37 1/2 = 75/2 minutes. Since it was open for 30 minutes, part of the cistern filled by pipe A =2/75 X 30 =4/5   So the remaining 1/5 part is filled by pipe B.   Pipe B can fill the cistern in 45 minutes. So, time required to fill 1/5 part   =45/5= 
<gadget id="calculator">45/5</gadget>
<output>9</output>
9 minutes.   i.e., pipe B is turned off after 9 minutes.   ANSWER IS 9 min
<result>B</result>
Two pipes A and B can fill a cistern in 37 1/2 minutes 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