Six bells commence tolling together and toll at intervals of 2, 4, 6, 8, 10, 12 minutes respectively. In 30 hours, how many times do they toll together?

All the clocks will toll together at the LCM of their intervals.

So LCM of the intervals = 2,4,6,8,10,12 = 120.


∴ all clocks will toll together after every 120 minutes.


Given interval = 30 hrs = 30 × 60 minutes = 1800 minutes {∵ 1hr = 60 minutes}


∴ number of times clock will tol = 1800/120 = 15.


plus one time when they commenced together


So the answer will be 16 times.


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