Question

three consecutive traffic lights change after 36,42&72 seconds. If the lights are first switch on at 9 am at what time will they change simultaneously?

Answer 1

Here, the question asks us 'at what time will they change simultaneously', which means that we need to find LCM.

36 = 2×2×3×3
42 = 2×3×7
72 = 2×2×2×3×3

So, LCM = 2×2×2×3×3×7
So, LCM = 504

Thus, the lights change after every 504 seconds.

And 504 s = 8 min 24 sec

So, the traffic lights will change again at 09:08:24 am

Answer 2

Here is your answer

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