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The Water Jug Puzzle

You have a 3-gallon jug and a 5-gallon jug. You have access to as much water as you need. How do you measure out exactly 4 gallons?

Solution

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**Step 1:** Fill the 5-gallon jug completely. **Step 2:** Pour from the 5-gallon jug into the 3-gallon jug until it's full. You now have 2 gallons left in the 5-gallon jug. **Step 3:** Empty the 3-gallon jug. **Step 4:** Pour the 2 gallons from the 5-gallon jug into the 3-gallon jug. **Step 5:** Fill the 5-gallon jug completely again. **Step 6:** Pour from the 5-gallon jug into the 3-gallon jug until it's full. Since it already has 2 gallons, it only takes 1 more — leaving exactly **4 gallons** in the 5-gallon jug.

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