You have 3 alarms in your room. your cell phone alarm is set to ring every 30 minutes. your computer alarm is set to ring every 20 minutes and your clock alarm is set to ring every 45 minutes. if all 3 alarms ring simultaneously at 12: 39pm., when is the next time they will ring simultaneously?

3:39 PM

Explanation:

Given

Cell phone Alarm is set to ring every 30 minutes

Computer alarm is set to ring every 20 minutes

Clock alarm is set to ring every 45 minutes

All alarms ring at 12:39 so next time they ring simultaneously is given by

LCM of (30, 20, 45)=180

Thus all alarms will ring simultaneously after 180 min i.e. at 3:39 PM

the use of electrical signals that transit messages is know as