Here is a 1 litre carton of milk, and beside it a solid cube that measures 10 cm along every edge.

Hands up: do you think these two hold the same amount of space inside, or is one bigger than the other?

Watch the two boxes and the converter on screen. The two boxes look completely different but hold the same amount — see if you can spot what stays the same. Then watch how one litre turns into millilitres, and think about what the very last step to cm³ should be.

Remember our rule: 1 ml fills exactly 1 cm³, so those numbers are always the same. When a job is written in cm³, we swap it for the same number of ml in our heads, then use the converter. Before we check each one, we say out loud whether we multiply or divide, and by what.

• 2,500 cm³ → litres
• 0.75 litre → millilitres
• 500 ml → litres
• 1.5 litres → millilitres

Today we work through these on the board. Say whether you multiply or divide before each one.

• 3,000 cm³ → litres
• 1.5 litres → millilitres
• 750 ml → litres
• Fish tank 30 cm × 20 cm × 25 cm. Work out its volume first, then say how many litres it holds.