# Two pipes P and Q can fill a cistern in 12 and 15 minutes respectively. Both are opened together, but at the end of 3 minutes, P is turned off. In how many more minutes will Q fill the cistern ? A.7 B.7$1\over2$ C. 8 D.8$1\over4$

 [ A ]    a [ B ]    b [ C ]    c [ D ]    d
 Answer : Option D Explanation :