Question

Five Bells commences tolling together and tolls at intervals 3, 6, 9, 12 and 15 seconds respectively. In 45 minutes, how many times do they toll altogether

Answer 1

Firstly we will find the LCM of 3, 6, 9, 12 15 is 180.

So, after each 180 seconds, they would toll together.

Hence, in 45 minutes, they would toll $=\frac{45 \times 60 seconds}{180 seconds}$ = 15 times

According to the question,"they commence tolling together". So, they basically also toll at the "beginning" which means at second.

So, total tolls together = 15+1 = 16 times.