Question

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

Answer 1

Three bells toll at intervals of 9, 12 and, 15 minutes.
The time when they will toll together again is given by the LCM of 9, 12, and 15.

Required time = 2² × 3² × 5
= 180 minutes
=3 h
If they start tolling together, they will toll together again after 3 h.