question_answer

Six bells commence tolling together and toll at intervals of 2 s, 4 s, 6 s, 8 s, 10 s, 12 s respectively. In 30 min, how many times to the toll together?

A) 4

B)  10     

C)  15

D)  16

Correct Answer: D

Solution :

LCM of 2, 4, 6, 8, 10, 12 \[=(2\times 2\times 3\times 2\times 5)=120\] After every 2 min they toll together. Number of times they toll in 30 min \[=\left( \frac{30}{2}+1 \right)\]times = 16 times