Question

Four bells toll together at 5,10,15,20seconds.If they rang at 4 pm. At what time they will toll again?

Answer 1

Step 1: Find LCM

5 = 5

10 = 2 x 5

15 = 3 x 5

20 = 2² x 5

LCM = 2² x 3 x 5 = 60 seconds

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Step 2: Find the time that they will ring again:

60 seconds = 1 min

4pm + 1 min = 4: 01 pm

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Answer: 4:01 pm

Answer 2

take out the lcm of seconds which is 60.
it means after 60 sec bell will rang together.
thus 60 sec= 1min
it will rang again together at 4:01pm