Five bells begin to ring together and they ring at intervals of 3, 4, 8, 12 and 15 seconds, respectively. How many times will they ring together at the same second in one hour excluding the one at the end?

30 times

Step-by-step explanation:

1) First finding LCM of 3,4,8,12,15

3 = 3x1

4 = 2x2

8 = 2x2x2

12 = 3x2x2

15 = 5x3

LCM = 2x2x2x3x5 = 120

The bells will ring together every 120 seconds

2) The number of times they will roll together in an hour = 3600/120 = 30