Answer 9: Use the 3-gallon as a subtractor 💧
Fill the 5-gallon jug. Pour it into the 3-gallon jug until it’s full. You have 2 gallons left in the 5-gallon jug. Empty the 3-gallon jug. Pour the 2 gallons into it. Refill the 5-gallon jug. Pour from it into the 3-gallon jug (which already has 2) until full, using only 1 gallon. You’re left with exactly 4 gallons in the 5-gallon jug.
