Question

on MG road,three consecutive traffic lights change after 36,42,&72seconds.If the light's are first switched on at 9:00am, at what time will they change simultaneously?​

Answer 1

they will change simultaneously at 9:08:24am

Answer 2

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

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