Density ρ is equal to mass m per unit volume v, or
ρ = m / v
Solve for volume:
v = m / ρ
(a) 890 g of copper, which has a density of 8.9 g/cm³, has a volume of
v = (890 g) / (8.9 g/cm³) = 100 cm³
100 g of zinc, with density 7.1 g/cm³, has a volume of
v = (100 g) / (7.1 g/cm³) ≈ 14.08 cm³
(b) The density of brass is then
ρ = (890 g + 100 g) / (100 cm³ + 14.08 cm³) ≈ 8.68 g/cm³
