Question

A red light flashes every 6 seconds a green light flashes every 15 seconds a blue light flashes every 21 seconds they have all flashed at the same time, after how many seconds will they all flash at the same time again??

Answer 1

Answer:

You can find this answer by taking L.C.M.

or

use logic,

Red light flashes once every 6 seconds, blue light flashes once every 10 seconds, so the next time the blue light flashes(20 seconds), the red light would have completed 18 seconds and the next time blue light flashes (30 seconds), the red light would also be flashed at the same time.

We got the interval and it will go on and on every 30 seconds

Step-by-step explanation:

Thank you