Brain Teaser - Warmup for Problem Solving

You have an unmarked 5 Liter jug and an unmarked 3 Liter jug as well as unlimited water. Using just this equipment, how can you measure out exactly 4 Liters of water?

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Solution:

• Step 1: Fill the 5 L jug with water.
• Step 2: Use the 5 L jug of water to fill up the 3 L jug,
  leaving the 5 L jug with 2 L of water.
• Step 3: Empty the 3 L jug and refill it with the remaining 2 L water in the 5 L jug.
• Step 4: Fill up the 5 L jug again, then use it to fill the 3 L jug,
  leaving the 5 L jug with exactly 4 L of water.