A alone can do a work in 14 days. B alone can do the same work in 28 days. C alone can do the same work in 56 days. They start the work together and completed the work such that B was not working on last 2 days and A did not work in last 3 days. In how many days (total) was the work completed?

Answer: Option A

Solution

Answer: Option A

Solution:

Work done not done by B = 2 × 2 = 4
Work done not done by A = 3 × 4 = 12
Total work = 56 + 4 + 12 = 72
∴ Total time $$=\frac{72}{4+2+1}=\frac{72}{7}\text{days}$$