Two pipes P and Q can fill a cistern in 10 and 25 minutes respectively. Both are opened together, but at the end of 5 minutes the first is turned off. How much longer will the cistern take to fill?
Choose the correct option:
A) 12 1/7
B) 12 1/4
C) 12 1/3
D) 12 1/2
E) 12 1/5
5/10+ x/25 = 1   x= 12 1/2 Answer: 12 1/2
<result>D</result>
Two pipes P and Q can fill a cistern in 10 and 25 minutes respectively. Both are opened together, but at the end of 5 minutes the first is turned off. How much longer will the cistern take to fill?