A, B and C can do a piece of work in 18, 24 and 36 days, respectively. They work alternately, first day C, second day B and third day A, fourth day C and so on. How many days will be needed to complete the work like this way?

Correct Answer: 24

Explanation:

Work done in first in 3 days
= (1/18) + (1/24) + (1/36) = (4 + 3 + 2)/72 = 1/8
∵ Time taken to complete 1/8 part of work = 3 days
∴ Time taken to complete the whole work = 3 x 8 = 24 days