Question

Three bells toll at intervals of 9, 12 and 15 minutes respectively. If they start tolling together, after what time will they next toll together?

Answer 1

It is given that three bells toll at the intervals of 9, 12, and 15 minutes, respectively.

We need to find out if they start tolling together and after what time they will next toll together.
LCM of 9, 12, 15 can be found as:
On doing factorization of 9, 12 and 15, we get,
9 = 3²
12 = 2² × 3
15 = 5 × 3
LCM can be written as = 3² × 2² × 5 = 180

Time = 180 minutes = 3 hours