Question
Wed June 29, 2011 By:

2 alarm clocks ring their alarms at regular intervals of 50 sec & 48 sec. If they beep together at 12 noon at what time will they beep again for the 1st time? a)12.20pm b)12.12pm c)12.11pm b)none of the these

Expert Reply
Wed June 29, 2011
Since the regular interval of alarms are 50s and 48s.
So both alarms ring together after x sec., where x is LCM of 50 and 48.
Now LCM(50, 48) =1200
So both alarms ring together after 1200 sec.
Or, both alarms ring together after 20 min.      (by dividing 60)
Now, since they beep together at 12 noon,
So next time they beep together at 12:20 PM.
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