Question

One computer in a lab is programmed to back up data at the turn of the minute every five minutes. Another computer is programmed to back up data at the turn of the minute every two minutes. Find the number of times in twenty-four hours that the two computers back up data at the same time.

(Assume that the computers do not back up at the start of the 24-hour period.)

Answer 1

Since the two computers back up at different intervals, we can find the least common multiple of the two intervals to determine how often they back up at the same time. The least common multiple of 5 and 2 is 10. Therefore, the two computers will back up at the same time every 10 minutes. In 24 hours, there are 60 minutes/hour * 24 hours = 1440 minutes. Dividing this by the interval of 10 minutes gives 1440 minutes / 10 minutes/backup = 144 backups. Therefore, the two computers will back up at the same time 144 times in 24 hours.

Explanation: