Question

A spotlight at a dance club flashes every 25 seconds. Another spotlight flashes every 30 seconds. Both lights just flashed . After how many minutes will both lights flash at the same time again?

Answer 1

find the least common multiple of 25 and 30, which is 150

 so they will flash at the same time every 150 seconds which equals 2.5 minutes

Answer 2

150 seconds for both the lights to flash.