Question

two alarm clock ring there alarms at regular intervals of 40 seconds and 30 seconds. if they first beep together at 12 noon,at what time will they beep again for the first time?

Answer 1

$the \: time \: in \: which \: both \: the \: clock \: will \: beep \: together \: is \: the \: lcm \: of \: 40 \: and \: 30 \: i.e \: 120......$

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