The traffic lights at three different road crossings change after every 48 seconds, 72 seconds and 108 seconds respectively.
Question:
The traffic lights at three different road crossings change after every 48 seconds, 72 seconds and 108 seconds respectively. If they all change simultaneously at 8 a.m. then at what time will they again change simultaneously?
Solution:
We find the LCM of 48, 72 and 108 first to get the time after which they will blink together again.
Hence, LCM $=2 \times 2 \times 2 \times 2 \times 3 \times 3 \times 3=432$
So, they will blink again at 432 seconds past 8:00 am
or, $\frac{432}{60}=7$ minutes and 12 seconds past $8: 00$ am
So, the time will be 08:07:12 hrs