Answer:
This problem is same as finding the least common multiple (LCM) of 3 and 4.
3 = 3
4 = 2 x 2
=> LCM = 3 x 2^2 = 12 (3 appears once, 2 appears twice)
=> After 12 hours, two bell P and Q ring simultaneously.
Hope this helps!
:)
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