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?

LCM(15,18) = 90

so what time is 90 minutes after 1:00 ?

To determine when the two lighthouses will next flash together, we need to find the least common multiple (LCM) of their flash intervals. The LCM is the smallest positive integer that is divisible by both flash intervals.

First, let's find the multiples of 15 minutes:
15, 30, 45, 60, 75, 90, 105, ...

Now, let's find the multiples of 18 minutes:
18, 36, 54, 72, 90, 108, ...

From the lists above, we can see that both lighthouses will flash together at 90 minutes (or 1 hour and 30 minutes) after they initially flash together at 1:00 A.M.

Therefore, they will next flash together at 2:30 A.M.

Pano to sagutan with solution