Question

A bell rings every $5$ seconds. A second bell rings every $6$ seconds and a third one rings every $8$ seconds. If all the three rings at the same time at $8.00$ a.m, at what time will they all ring together next?

• A. $1$ minute past $8.00$ a.m.
• B. $2$ minute past $8.00$ a.m.
• C. $3$ minute past $8.00$ a.m.
• D. $4$ minutes past $8.00$ a.m.

Answer 1

The correct option is B $2$ minute past $8.00$ a.m.

The LCM of $5$ sec, $6$ sec and $8$ sec is the next time all the $3$ bells would ring together.
The LCM of $5,6,8$ is $120$ sec.
$120$ sec = $2$ minutes.
So, the next time they will ring together is at $8:02$ am.