A cistern is normally filled in 8 hours but takes two hours longer to fill because of a leak in its bottom. If the cistern is full, the leak will empty it in? Answers
A) 27
B) 20
C) 40
D) 73
E) 72

Rationale: "1 / 8 - 1 / x = 1 / 10 x = 40 answer : c"
Answer: C