# Calculating volume

Volume is a measure of space taken up by a 3-dimensional shape and is measured in $$mm^{3}$$, $$cm^{3}$$ etc.

Volume can also be measured in litres with $$1\, litre = 1000\,cm^{3}$$.

Make sure you don't confuse volume (for 3-D shapes) and area (for 2-D shapes).

## Converting units

To convert litres to $$cm^{3}$$, we multiply by $$1\,000$$.

$5\; litres = 5 \times 1\,000 = 5\,000cm^{3}$

$$23.6\; litres = 23.6 \times 1000 = 23\,600cm^{3}$$3

To convert $$cm^{3}$$ to litres, we divide by $$1\,000$$.

$8\,000cm^{3} = 8\; litres$

$125\, 000cm^{3} = 125\; litres$

$7\,530cm^{3} = 7.53\; litres$

Question

Sam is going to buy some cola for her son’s birthday party. The cola comes in one-litre bottles. The plastic cups she has each hold about 90 millilitres. 14 children have been invited and Sam reckons about 3 cups each would be appropriate over the afternoon.

How many one-litre bottles should she buy?

$Amount\,for\,1\,child = 90 \times 3 = 270ml$

$Amount\,for\,14\,children = 270 \times 14 =3\,780\,ml$

One litre is $$1\,000\,ml$$ so Sam needs to buy $$4$$ one-litre bottles.