there are 3 alarms A, B , C.A rings after every 3 hrs, B rings after every 4 hrs and C rings after every 6 hrs.Find the time interval after which the 3 alarms ring together after ringing once.

We need to find the time at which all the 3 alarms will ring at the same time, hence we need to find the lowest common multiple of the time intervals of the 3 alarams i.e. LCM (3,4,12) = 12

 

Hence, the three alarms will ring together at every 12 hour intervals.