The density of an object is given by:
D = M/V
D = density, M = mass, V = volume
The volume of the cube V is given by:
V = s³
where s = side length
Make a substitution:
D = M/s³
Given values:
M = 20kg, s = 20×10⁻²m
Plug in and solve for D:
D = 20/(20×10⁻²)³
D = 2500kg/m³