A and B can reap a field in 30 days, working together. After 20 days, however, B is called away and A takes 20 days more to complete the work. B alone could do the whole work in
- 48 days
- 50 days
- 56 days
- 60 days
- 64 days
(A + B)'s 20 day's work = (1/30 Γ 20) = 2/3
Remaining work = (1 - 2/3) = 1/3
Now, 1/3 work is done by A in 20 days.
Therefore, the whole work will be done by B in 20 Γ 3 = 60 days.