The mass of a cube is directly proportional to the cube of its side

Question

The mass of a cube is directly proportional to the cube of its side

Answer 1

M=ro*V,  ro - density,  V- volume.
V=a^3      a- side.
M=ro*a^3   

Answer 2

M=p*v=p*a^3 а значит пропорционален