Question

lighthouse 1 flashes its light every 15 minutes. Lighthouse 2 flashes every 18 minutes. If the two lighthouses flash together at 1:00 A.M, what time they will next flash together?

Answer 1

LCM(15,18) = 90
so what time is 90 minutes after 1:00 ?

Answer 2

Pano to sagutan with solution