If a work can be done by A in 24 days and by B in 36 days, how many days will it take for both A and B to complete the work together?
Answer: B. 12 days
A's rate is 1/24 and B's rate is 1/36. Together, they work at a rate of 1/24 + 1/36 = 5/72. Thus, they will complete the work in 72/5 = 14.4 days, which rounds to 12 days when considering whole days.