**Density** is the amount of mass in a volume. The more dense a substance is, the heavier it is for the same amount of volume.

The formula for density is:

`text(density) = frac(text(mass))(text(volume))`

Density is measured in g/cm^{3} or kg/m^{3}.

A cuboid of lead, 3cm by 5cm by 2cm, has density of 11.34 g/cm^{3}. What mass is the cuboid?

Volume = 3 x 5 x 2 = 30cm^{3}.

Cover up mass: left with density x volume

30 x 11.34 = 340.2g

Answer: 340.2g

The density of water is 1000 kg/m^{3}. A swimming pool has been constructed on the top of a building. The swimming pool is 1.5m deep throughout, and is 10m by 15m. What mass of water will be contained within the pool?

The volume of the pool is 1.5 x 10 x 15 = 225m^{3}.

From the triangle, cover up mass: left with density x volume:

225 x 1000 = 225000Kg, os 225 tonnes.

Answer: 225 tonnes

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