A and B together can do a piece of work in 24 days. A alone can do this work in 40 days. In how many days can B alone do this work?

Let's assume the total work is 120 units.

A and B together can do a piece of work in 24 days.

Efficiency of A and B together = $$\frac{120}{24}$$ = 5 units/day

A alone can do this work in 40 days.

Efficiency of A = $$\frac{120}{40}$$ = 3 units/day

Efficiency of B = Efficiency of A and B together - Efficiency of A

= 5 units/day - 3 units/day

= 2 units/day

Time taken by B alone to do this work = $$\frac{120}{2}$$

= 60 days