Two pipes A and B can fill a cistern in 37 ½ min and 45 minutes respectively. Both the pipes are opened. The cistern will be filled in just half an hour, if the pipe B is turned off after Choices:
A) 6 minutes
B) 9 minutes
C) 45 minutes
D) 3 minutes
E) 4 minutes
If pipe 9 minutes is turned off after x mins, then   (2*30)/75 + x/45 =1   x/45 = 1-60/75 = 1/5   x= 45/5= 
<gadget id="calculator">45/5</gadget>
<output>9</output>
9 mins   ANSWER:9 minutes
<result>B</result>
Two pipes A and B can fill a cistern in 37 ½ min and 45 minutes respectively. Both the pipes are opened. The cistern will be filled in just half an hour, if the pipe B is turned off after