How can you measure exactly 5 gallons only using 2 containers that are 3 gallons and 4 gallons?
1. Completely fill the 4 gallon container. 2. Pour 3 of the 4
gallons into the 3 gallon container, leaving 1 gallon in the 4
gallon container. 3. Empty the 3 gallon container and pour the 1
remaining gallon from the 4 gallon container into the 3 gallon
container. 4. Fill the 4 gallon container. Now you have a total of
5 gallons, 4 in the 4 gallon container and 1 in the 3 gallon.