An indoor water park has two giant buckets that slowly fill with 1000 gallons of water before dumpin

An indoor water park has two giant buckets that slowly fill with 1000 gallons of water before dumping it on the people below. One bucket dumps water every 18 minutes. The other bucket dumps water every 21 minutes. It is currently 1:15 P.M. and both buckets dumped water 5 minutes ago. Find the next two times that both buckets dump water at the same time.

We want to find the Least Common Multiple between 18 minutes and 21 minutes. This shows us when both bucket dumping cycles happen simultaneously. So we type in LCM(18,21) into our search engine and we get:
LCM(18, 21) = 126

This means, in 126 minutes, both buckets will dump water. Since 60 minutes is in an hour, we find out how many full hours we have. To find the full hours and remainder, we type in 126 mod 60 into our search engine and we get:
6. This means 126 minutes is 2 hours and 6 minutes.

Find the next bucket dumping time:

1. We start at 1:15 PM
2. Add 2 hours and we get 3:15 PM
3. Add 6 minutes and we get 3:21 PM