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)

$16$

L.C.M. of $2$, $4$, $6$, $8$, $10$, $12$ is $120$.
So, the bells will toll together after every $120$ seconds ($2$ minutes).
In $30$ minutes, they will toll together $\frac{30}{2}+1=16$.