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Three bells start ringing after interval of 20 minutes, 25 minutes and 40 minutes. They ring simultaneously at 8:00 am. They will ring simultaneously
Question

Three bells start ringing after interval of 20 minutes, 25 minutes and 40 minutes. They ring simultaneously at 8:00 am. They will ring simultaneously again at

A.

9:00 am

B.

10:00 am

C.

11:20 am

D.

12:20 pm

Correct option is C

Given:

Three bells ring at intervals of 20 minutes, 25 minutes, and 40 minutes.

They ring together at 8:00 AM. Find the next time they will ring simultaneously.

Solution:

Prime factorization:

20 = 22×52^2 \times 5​​

25 = 525^2​​

40 = 23×5 2^3 \times 5​​

LCM = 23×52=8×25 2^3 \times 5^2 = 8 \times 25​ = 200 minutes

Convert 200 minutes:

200 = 3 hours 20 minutes

Add to given time:

8:00 AM + 3:20 = 11:20 AM

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