ρ = m \Rightarrow m = ρ V = 0, 9 \frac{g}{c m^{3}} \cdot 21 c m^{3} = 19 g

${\rho = m \Rightarrow m = \rho V = {0,9}\,\mathrm{\frac{g}{cm^3}}\cdot {21}\,\mathrm{cm^3} = {19}\,\mathrm{g}}$

Error