A, B and C can do a piece of work in 24 days, 30 days and 40 days respectively. They began the work together but C left 8 days before the completion of the work. In how many days was the work completed?
Select:
A) 12 days B) 16 days C) 18 days D) 11 days E) 38 days

Rationale: "one day work of a , b and c = 1 / 24 + 1 / 30 + 1 / 40 = 1 / 10 work done by a and b together in the last 8 days = 8 * ( 1 / 24 + 1 / 30 ) = 3 / 5 remaining work = 2 / 5 the number of days required for this initial work = 4 days . the total number of days required = 8 + 4 = 12 days . answer : a"
Answer: A