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?	Pick one.
A) 76 hrs
B) 70 / 3 hrs
C) 55 hrs
D) 90 hrs
E) 11 hrs

Rationale: 1 / 7 - 1 / x = 1 / 10 = > 70 / 3 hrs answer : b
Answer: B