Question

The traffic lights at three different road – crossing change after every 36 seconds,
60 seconds and 72 seconds. If they change simultaneously at 8 a. m. after, what time
will they change again simultaneously?

Answer 1

Consider the problem

The traffic light at three different road crossing change after every 48seconds,72seconds and 108seconds respectively

So,

48=2×2×2×2×372=2×2×2×3×3108=2×2×3×3×3

Therefore, L.CM of 48,72,108 is 

(2×2×2×2×3×3×3)=432

So, time when they change again =432seconds

But we need to find time after 7am So,

first we convert 432seconds into minutes. 

Time=432second=60432minutes∴Time=7 minutes12 seconds

 

Thus,

Required time =7am+7minutes 12seconds

=7:07:12am

Answer 2

Here is the correct answer of your question:-

In order to solve such questions you need to take the LCM of the given numbers

Hence LCM of 36, 60,72 is = 360 seconds

In minutes it will be 360÷60=6 mins

Hence they will change again at 8:06 a.m

Hope this helps you ❤️