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?

Question

Accepted Answer

Step 1: $9 = 3^2$, $12 = 2^2 	imes 3$, $15 = 3 	imes 5$
Step 2: LCM $= 2^2 	imes 3^2 	imes 5 = 180$. Three bells will toll together after $180$ minutes.

Question

Solution