Four bells begin to toll together and toll respectively at intervals of 6, 7, 8 and 9 seconds. In 1.54 hours, how many times do they toll together and in what interval (seconds)?

A. 14, 504

B. 14, 480

C. 12, 504

D. 16, 580

Answer: Option C

Solution(By Examveda Team)

Interval after which the bells will toll together = (LCM of 6, 7, 8, 9) sec = 504 sec.
In 1.54 hours, they will toll together
$$\eqalign{ & {\text{ = }}\left[ {\left( {\frac{{1.54 \times 60 \times 60}}{{504}}} \right) + 1} \right] \cr & {\text{ = 12 times}} \cr} $$