Correct option is B
Given:
Four bells ring at the intervals of 5, 6, 8 and 9 seconds respectively.
All the bells ring simultaneously at some time.
Concept:
The Least Common Multiple (LCM) of the time intervals at which they ring.
Solution:
Bell 1: 5 seconds
Bell 2: 6 seconds
Bell 3: 8 seconds
Bell 4: 9 seconds
Bell 2: 6 seconds
Bell 3: 8 seconds
Bell 4: 9 seconds
5 = 5
6 = 2 × 3
8 = 2 × 2 × 2
9 = 3 × 3
LCM = 5 × 2 × 2 × × 2 × 3 × 3 = 360 seconds
360 seconds = 6 minutes
So, They will again ring simultaneously after 6 minutes.
Thus, the correct answer is (b).
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