Question

Six bells commence tolling at the intervals of 2, 4, 6, 8, 10 and 12 seconds respectively. How many times do they toll together in an hour?

Answer 1

LCM of 2, 4, 6, 8 10 and 12 is 120.

So, after each 120 seconds, they would toll together.

Hence, in 30 minutes, they would toll 30*60 seconds / 120 seconds = 15 times

But then the question says they commence tolling together. So, they basically also toll at the "beginning" ("0" second).

So, total tolls together = 15+1 = 16