So if the red light blinks every 3 seconds and the blue light blinks every 5 seconds, I can indicate that they must both go into something for them to blink at the same time.
So, 3 × 5 = 15. Every 15 seconds they will blink.
There are 60 seconds in a minute, so just divide 60 by 15 to get your answer.
Which will be 4.
The red and blue light will blink 4 times in a minute at the same time.
