A pipe can fill a cistern in 14 minutes whereas the cistern when fill can be emptied by a leak in 28 minutes. When both pipes are opened, find when the cistern will be full?	Pick one
A) 17
B) 16
C) 28
D) 13
E) 12
1/14 - 1/28 = 1/28   28 minutes   Answer: 28
<result>C</result>
A pipe can fill a cistern in 14 minutes whereas the cistern when fill can be emptied by a leak in 28 minutes. When both pipes are opened, find when the cistern will be full?