A and B can complete a work in 24 days together. If A alone can do it in 36 days, how long will B take to complete the work alone?
Answer: A. 48 days
If A can do the work in 36 days, A's work rate is 1/36. The combined work rate is 1/24, so B's work rate is 1/24 - 1/36 = 1/72. Therefore, B can complete the work alone in 72 days.