A light house has two lights one that flashes every 3 minutes and another that flashes every 3 and a half minute suppose the light flash together at noon what is the first time after 2 p.m. that will they will flash together again

Answer 1

the 1/2 minutes will add up to another 3.5 minutes after 7 3-minute cycles
So, at 2:21 they will both blink again.