Question

traffic light at three different road crossing changed after 48,72,108 seconds if they changsimultaneously at7 am what time they change simultaneously again

Answer 1

First take out the LCM of 48,72 and 108 seconds.
That is 432 seconds
Now divide 432 by 60 in order to get a proper time.
The quotient will be the minutes and the remainder will be the seconds
So It will be 7 minutes and 12 seconds
Now add this to 7 am 
The time will be 7:7:12 am

I hope this helps......