Question

We observed the traffic lights at three different squares on the same big road. They turn green every 60 seconds, 120 seconds and 24 seconds. When the signals were switched on at 8 o’clock in the morning, all the lights were green. How long after that will all three signals turn green simultaneously again?

Answer 1

Answer-

After 2 minutes or at 8.02 all the lights will turn green simultaneously.

Solution-

Three traffic lights turn green every 60 seconds, 120 seconds and 24 seconds.

They will change simultaneously after a time which is a common multiple of 24, 60 and 120 seconds.

LCM (24, 60 and 120 seconds) = 120 seconds = 2 minutes

Therefore, after 2 minutes or at 8.02 all the lights will turn green simultaneously.