lets assume
L = length of the object = 5 cm
h = height of the object = 3 cm
w = width of the object = 2 cm
V = Volume of the object
Since the dimensions of object suggest it to be a cuboid
Volume of the object is given as
V = L w h
inserting the values
V = 5 x 3 x 2
V = 30 cm³
m = mass of the object given = 10 g
ρ = density of the object = ?
density of the object is given as
density of object = mass of object / Volume of object
ρ = m/V
inserting the values
ρ = 10/30
ρ = 0.33 g/cm³