Question

A can complete a job in 12 days and B in 18 days. They work together for 4 days, then A leaves. How many more days will B need?

Solution

1. Together, one-day work = 1/12 + 1/18 = 5/36.
2. Work done in 4 days = 4 x 5/36 = 5/9.
3. Remaining work = 1 - 5/9 = 4/9.
4. B completes 1/18 per day, so time needed = (4/9) x 18 = 8 days.