A, B and C can do a piece of work in 7 days, 14 days and 28 days respectively. How long will they take to finish the work, if all the three work together?\nOptions:\n(A) 4\n(B) 9\n(C) 2\n(D) 11\n(E) None
Let’s work this out in a step by step way to be sure we have the right answer.
(A)
1/7 + 1/14 + 1/28 = 7/28 = 1/4\nAll three can finish the work in 4 days.

The answer is (A)