Question

Six bells commence tolling together and toll at intervals of 2,
4, 7, 8, 10 and 12 seconds respectively. In 30 minutes how
many times do they toll together?
1) 24 - 2 20 3) 12 4) 16​

Answer 1

Obesity all the five Bells will toll together after an interval which is the multiple of 4,7,8,10,12 seconds respectively.

LCM of 4, 7, 8, 10 and 12 =840

therefore the time when they will next toll together is equal to 840 seconds.

Hence, the number of times they will strike together in 30 minutes=(30*60)/840 sec