Two alarm clocks ring their alarms at regular intervals of 50 seconds and 48 seconds. If they first beep together at 12 noon, at what time will they beep again for first time?

Explanation:-

They will ring together after,
LCM of 48 and 50 secs.
48 = 2*2*2*2*3;
50 = 2*5*5;
LCM = 2*2*2*2*3*5*5 = 1200 secs
= 20 min.
They will beep together at 12:20.