Question

Question #d9611

Answer 1

It is not a question of physics but a question of simple arithmatics.

Given that three different coloured light bulbs on a display panel light up every 14,20,24 seconds respectively.
They all lit up together at 7.00. To determine the minimum time after which they will lit up together again we are to calculate the LCM of 14,20,24 sec.

`14=2xx7`

`20=2^2xx5`

`24=2^3xx3`

`"The LCM is" =2^3xx3xx5xx7=840s=840/60=14min`

So after 14min i.e. at 7 past 14 the lights will lit up together.