# A solid plastic cube has a side length of 4 cm. The mass of the cube is 80 g. What is the density of the plastic in grams per cubic centimetre?

${\rho}_{\text{plastic cube}} = \frac{5}{4} \cdot g \cdot c {m}^{-} 3. \ldots \ldots \ldots . .$
By definition, $\rho = \text{Mass"/"Volume} = \frac{80 \cdot g}{4 \cdot c {m}^{3}} = \frac{80 \cdot g}{64 \cdot c {m}^{3}}$
$= \frac{5}{4} \cdot g \cdot c {m}^{-} 3. \ldots \ldots \ldots \ldots \ldots .$