Four bells toll at intervals 4, 7, 12 & 84 seconds. The bells toll...
To find the least common multiple (LCM) of 4, 7, and 12, we can list the multiples of each number and find the smallest number that appears in all three lists:
Multiples of 4: 4, 8, 12, 16, 20, 24, 28, 32, 36, 40, 44, 48, 52, 56, 60, 64, 68, 72, 76, 80, 84, 88, 92, 96, 100, ...
Multiples of 7: 7, 14, 21, 28, 35, 42, 49, 56, 63, 70, 77, 84, 91, 98, 105, ...
Multiples of 12: 12, 24, 36, 48, 60, 72, 84, 96, 108, ...
From the lists, we can see that the smallest number that appears in all three lists is 84. Therefore, the four bells will toll together at every 84 minutes.