A is 50% more efficient than
B. A and B together can complete a piece of work in 20 days. Both of them started working together and worked for 12 days, after which B left and C joined
A. The remaining work was completed by A and C together in 5 days. In how many days can C alone complete the entire work?

Ratio of efficiency of A to B = 150 : 100 = 3 : 2 Let efficiency of B = 2 units/day and efficiency of A = 3 units/day Amount of work done by A and B together in one day = 3 + 2 = 5 units Total work = 5 × 20 = 100 units Amount of work done by A and B together in 12 days = 5 × 12 = 60 units Remaining work = 100 – 60 = 40 units Amount of work done by A and C together in one day = 40/5 = 8 units Amount of work done by C alone in one day = 8 – 3 = 5 units Time taken by C alone to complete the total work = 100/5 = 20 days So, C alone can complete the entire work in 20 days. Hence, the correct answer is C.