Question

Six bells commence tolling together and toll at intervals of $2,4,6,8,10$ and $12$ seconds respectively. In $30$ minutes, how many times do they toll together?

• A. $4$
• B. $10$
• C. $15$
• D. $16$

Answer 1

Answer: (D)

$16$

Since, LCM of $2,4,810$ and $12$ is $120$. So, after each $120$ seconds, they would toll together,

Hence, in 30 minutes, they would toll $\frac{30\times 60}{120}=15$ times
But then the question says they commence tolling together. So, they basically also toll at the beginning. So, total tolls together $=15+1=16$