Two neon lights are turned on at the same time

Question 3. Two neon lights are turned on at the same time. One blinks every 4 seconds and the other blinks every 6 seconds. Answer the following questions, give your answer only.

a) How long will it take them to blink simultaneously for the first time after they are turned on? (simultaneously: at the same time)

b) How many times will they blink simultaneously in the first 70 seconds after they are turned on?