Question

Four bells commence tolling together and toll at the intervals of 3,9,12,15 seconds resp. in 60 minutes how many times they will toll together? select one:

a. 20

b. 21

c. 30

d. 24

Answer 1

Answer:LCM of 3,9,12,15 is 180 sec.

180/60=3minutes

In 60 minutes

60/3+1=20+1=21

Step-by-step explanation:

And is b)21

Answer 2

Answer:

They will toll together for option (c) 30 times in 60 minutes with their respective  intervals of 3, 9, 12 and 15 seconds.

Step-by-step explanation:

Tolling time of:

first bell = 3 seconds

second bell = 9 seconds

third bell = 12 seconds

fourth bell = 15 seconds

For the first time they will toll together at the least common multiple of their tolling times.

LCM = 3 × 3 × 4 × 5 = 180 seconds = 2 minutes.

This means that in 60 minutes, they will toll together for = 60 / 2 times = 30 times.

Therefore, they will toll together for option (c) 30 times in 60 minutes.

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