If A and B together can complete a piece of work in 15 days and B alone in 20 days, then in how many days can A alone complete the work?
If A and B together can complete a piece of work in 15 days and B alone in 20 days, then in how many days can A alone complete the work?
Explanation
B alone can complete the work in 20 days, so B's work rate is 1/20 of the work per day.
A and B together can complete the work in 15 days, so their combined work rate is 1/15 of the work per day.
Since B's work rate is 1/20, A's work rate can be found by subtracting B's work rate from their combined work rate: (1/15 - 1/20) = 1/60 of the work per day.
Therefore, A alone can complete the work in 60 days.
So, the correct answer is: 60 days.