How to judge whether a copper ball is solid or hollow?

Example: The mass of the copper ball is 178g and the volume is 40 cubic centimeters. Is it hollow or solid? (Explain in three ways)

1) quality method:

If the copper ball is solid, its mass m should be:

M = v * ρ = 40 * 8.9g = 356g。

But in fact, the mass is only 178g, so it is hollow.

2) Volume method

If the copper ball is solid, its volume v is:

V=m/ρ= 178/8.9=20 cubic centimeters.

But the actual volume is 40 cubic centimeters, so it is hollow.

3) Density method

If a copper ball is solid, its density is:

ρ = m/v = 178/40 = 4.45g/cm3。

Obviously, the density less than copper is 8.9 g/cm3.

Therefore, it can only be hollow

Hope to adopt!