Question

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

Answer 1

Solution:
9 = 3 x 3 = 3²
12 = 2 x 2 x 3 = 2² x 3
15 = 3 x 5
=> LCM (9, 12, 15) = 2² x 3² x 5 = 180
=> the bells will toll together after 180 minutes.