A and B can complete a work together in 15 days. They work together for 3 days, then A leaves. If B alone completes the remaining work in 16 days, in how many days can A alone complete the whole work? MCQ with Answer and Explanation

Let the total work be 60 units. Combined efficiency of A and B = 60 / 15 = 4 units/day. In 3 days, they complete 3 * 4 = 12 units. Remaining work = 60 - 12 = 48 units. B completes 48 units in 16 days, so B's efficiency = 48 / 16 = 3 units/day. A's efficiency = 4 - 3 = 1 unit/day. Time taken by A alone = 60 / 1 = 60 days.