Puzzle: You have a 3-liter and a 5-liter water container, and neither one is marked aside from the total volume. A tap is also now flowing. In order to measure out exactly 4 liters of water, we must utilize the containers and the tap in the right way. How is this possible?

Pouring Water

Solution:

Measuring out exactly 4 liters of water using a 3-liter and a 5-liter container and a tap involves the following steps:

Pouring Water

• Fill the 3-liter container from the tap.
• Pour the 3 liters of water from the 3-liter container into the 5-liter container.
• Fill the 3-liter container again.
• Again pour the water from the 3-liter container into the 5-liter container until full. This will ensure that there is exactly 1 liter of water left in the 3-liter container.
• Discard the water from the 5-liter container.
• Pour 1 liter of water from the 3-liter container into the 5-liter container.
• Fill the 3-liter container completely using the tap again.
• Pour the water from the 3-liter container into the 5-liter container until the former is empty.

The above procedure will ensure exactly 4 liters of water in the 5-liter container.