A cistern which could be filled in 7 hours takes one hour more to be filled owing to a leak in its bottom. If the cistern is full in what time will the leak empty it?	Choose the correct choice from the following.
A) 76 hrs	B) 70/3 hrs	C) 55 hrs	D) 90 hrs	E) 11 hrs
1/7 - 1/x = 1/10   =&gt; 70/3 hrs   Answer: 70/3 hrs
<result>B</result>
A cistern which could be filled in 7 hours takes one hour more to be filled owing to a leak in its bottom. If the cistern is full in what time will the leak empty it?