A pipe can fill a cistern in 20 minutes whereas the cistern when fill can be emptied by a leak in 30 minutes. When both pipes are opened, find when the cistern will be full?
Choose the most appropriate option.
A) 17 minutes	B) 87 minutes	C) 60 minutes	D) 27 minutes	E) 11 minutes
1/20 - 1/30 = 1/60   60 minutes   Answer:60 minutes
<result>C</result>
A pipe can fill a cistern in 20 minutes whereas the cistern when fill can be emptied by a leak in 30 minutes. When both pipes are opened, find when the cistern will be full?