Write down an equation which defines density

(i) Write down an equation which defines density.
(ii) If a 4 kg of material A occupy 20 ${{cm}^{3}}$ 18 kg of material B occupy 90 ${{cm}^{3}}$.
Which has the greater density A or Support your answer with calculations.

(i)We know that , density = Mass/ Volume
(ii)Density of Material of ,A = Mass of A / Volume of A = 4 x ${{10}^{3}}$ / 20 ${{cm}^{3}}$ = 200 g ${{cm}^{-3}}$
Density of Material , B =Mass of B / Volume of B = 18 x ${{10}^{3}}$ / 90 ${{cm}^{3}}$ = 200 g ${{cm}^{-3}}$
Both A and B have same densities.