An alarm clock rings regularly every 8 hours, while another one rings every 9 hours. If the two alarms ring simultaneously at 12 o'clock, after how many hours will they ring simultaneously again?
Find the smallest number of hours that is both a multiple of 8 and a multiple of 9. (Do not include 0.)
8 and 9 do not share any common factors, so multiply 8 and 9 to find the number of hours.
So, the two alarms will ring simultaneously again in 72 hours.