A cistern is filled by a tap in 5 1/2 hours. Due to leak in the bottom of the cistern, it takes half an hour longer to fill the cistern. If the cistern is full how many hours will it take the leak to empty it?
Choose the correct choice from the following choices: A) 60 B) 62 C) 64 D) 66 E) 68
filling rate - leak rate = net rate   1/5.5 - leak rate = 1/6   leak rate = 2/11 - 1/6 = 1/66   The answer is 66.
<result>D</result>
A cistern is filled by a tap in 5 1/2 hours. Due to leak in the bottom of the cistern, it takes half an hour longer to fill the cistern. If the cistern is full how many hours will it take the leak to empty it?