The mass of an iron ball is 312 g. The density of iron is 7.8 g cm^-3. Find the volume of the ball.

Mass = 312 g
Density = 7.8 g cm^-3
Volume = ?

$\text{Density} = \dfrac{\text{Mass}}{\text{Volume}} \\[1em] \text{7.8} = \dfrac{\text{312}}{\text{Volume}} \\[1em] \text{Volume} = \dfrac{\text{312}}{\text{7.8}} = 40 \text{cm}^{3}$

So, volume of the ball is 40 cm³.