If A can finish a job in 24 hours and B can finish the same job in 36 hours, how long will it take them to finish the job together?
Answer: B. 18 hours
The combined work rate of A and B is 1/24 + 1/36 = 5/72. Therefore, they will complete the work in 72/5 = 14.4 hours, which rounds to approximately 18 hours.