Two pipes A and B can fill a cistern in 75/2 minutes and 45 minutes respectively. Both pipes are opened. The cistern will be filled in just half an hour, if the B is turned off after:	Select:
A) 5 min.
B) 9 min.
C) 10 min.
D) 15 min
E) 18 min
If 9 min. is closed after x mins, then   30*2/75 + x/45 = 1   x/45 = 1 - 4/5 = 1/5   x= 45/5= 
<gadget id="calculator">45/5</gadget>
<output>9</output>
9 mins   ANSWER:9 min.
<result>B</result>
Two pipes A and B can fill a cistern in 75/2 minutes and 45 minutes respectively. Both pipes are opened. The cistern will be filled in just half an hour, if the B is turned off after: