A lighthouse flashes its light every 12 minutes. Another lighthouse every 18 minutes. If the two lighthouses flash together at 12:00 noon,at what time will they next flash together?

Answer 1

Easy way: from a start at 0,
first lighthouse flashes at 12,24,36,48,60,72,84,... minutes
2nd lighthouse flashes at 18,36,....
so my "guess" would be at 12:36
(that was too easy)

rigorous math approach
12 = 2*2*3
18 = 2*3*3
LCM = 2*2*3*3 = 36
so time is 12:36

btw, a lighthouse that flashes only every 18 minutes would
be useless and downright dangerous to depend on.
Are you sure it wasn't seconds? The solution would then be
12:00:36

Answer 2

Bobo ampota