Two pipes P and Q can fill a cistern in 10 and 15 minutes respectively. Both are opened together, but at the end of 2 minutes the first is turned off. How many more minutes will it take for the cistern to fill after the first pipe is turned off?	Select:
A) 6  B) 7  C) 8  D) 9  E) 10
Let x be the total time it takes for the cistern to fill.   2/10 + x/15 = 1   x/15 = 4/5   x = 12   After the first pipe is turned off, it takes 10 more minutes to fill the cistern.   The answer is 10.
<result>E</result>
Two pipes P and Q can fill a cistern in 10 and 15 minutes respectively. Both are opened together, but at the end of 2 minutes the first is turned off. How many more minutes will it take for the cistern to fill after the first pipe is turned off?