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 6 days before the completion of the work. In how many days was the work completed?  Choose the most appropriate option:	A) 12 days	B) 16 days	C) 18 days	D) 11.5 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 6 days = 6 * ( 1 / 24 + 1 / 30 ) = 9 / 20 remaining work = 11 / 20 the number of days required for this initial work = 5.5 days . the total number of days required = 6 + 5.5 = 11.5 days . answer : d"
Answer: D