Two patrol boats leave port together, one returning every 8 hours and the other every 10 hours. If both leave together at noon, after how many hours will they next leave together?

Correct answer to question 237 (Arithmetic Reasoning): 40 hours

Method

The boats align again at a common multiple of their cycles, and the soonest time is the least common multiple. The multiples of 8 are 8, 16, 24, 32, 40, and 40 is the first that 10 also divides, so they next leave together after 40 hours.