Two pipes P and Q can fill a cistern in 12 and 10 minutes respectively. Both are opened together, but at the end of 3 minutes the first is turned off. How much longer will the cistern take to fill? Choose the correct choice from the following
A) 1/8	B) 1/2	C) 2/4	D) 1/4	E) 1/4
3/12 + x/10   = 1   x= 8 1/2   Answer: 1/2
<result>B</result>
Two pipes P and Q can fill a cistern in 12 and 10 minutes respectively. Both are opened together, but at the end of 3 minutes the first is turned off. How much longer will the cistern take to fill?