# Measure exactly 4 litres: visual puzzle | SwaVid

You have an empty 3 L jug and an empty 5 L jug. How can you measure exactly 4 L of water? See the complete step-by-step solution.

Canonical: https://www.swavid.com/puzzles/water-jugs

Source: https://www.swavid.com/puzzles/water-jugs

# Measure exactly 4 litres

## Fill the 5, pour into the 3, empty the 3, pour the 2 across, refill the 5, top up the 3. The 5 L jug holds 4 L.

### Make 2 litres

### Move the 2 litres

### Top up

SwaVid visual puzzle

You have an empty 3 L jug and an empty 5 L jug. How can you measure exactly 4 L of water?

Detailed solution

The 3 L jug is a tool for removing water from the 5 L jug in known amounts.

Fill the 5 L jug and pour into the 3 L jug until it is full. The 5 L jug now holds 2 L.

Empty the 3 L jug and pour the 2 L into it. The 3 L jug now has 1 L of space left.

Fill the 5 L jug again and pour into the 3 L jug until it is full. Only 1 L leaves, so 4 L remains.

Trying to reach 4 by filling and pouring only once. You need to use the leftover 2 L from the first pour.

- 1 Make 2 litres Fill the 5 L jug and pour into the 3 L jug until it is full. The 5 L jug now holds 2 L. 5 − 3 = 2
- 2 Move the 2 litres Empty the 3 L jug and pour the 2 L into it. The 3 L jug now has 1 L of space left. 3 − 2 = 1 L of space
- 3 Top up Fill the 5 L jug again and pour into the 3 L jug until it is full. Only 1 L leaves, so 4 L remains. 5 − 1 = 4

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