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Question
Three bells toll together at intervals of 9, 12, 15 minutes. If they start tolling together, after what time will they next toll together?
Options
1 hour
- \[1\frac{1}{2}\] hours
- \[2\frac{1}{2}\] hours
3 hours
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Solution
3 hours
The L.C.M. of 9, 12, and 15 will give us the minutes after which the bells will next toll together.

L.C.M. = 22 × 32 × 5
= 180
So, the bells will toll together after 180 min.
On converting into hours:
180/60 = 3 hours
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