Measure 5 Liters

Solution

Use the [3L] and [4L] cans. 1. Fill [4L] with water. 2. Fill [3L] from [4L]. 3. Empty [3L]. 4. Pour the remaining water from [4L] into [3L]. 5. Fill [4L] with water. There are 5L of water: 1L in [3L] plus 4L in [4L].