Excuse me, I accidentally post the answer in the request of question
clarification box, now I am posting it in the correct place. Please,
forgive my mistake.
First a useful notice:
"To determine the density of any substance, one needs to know the mass
and volume of the sample.
The mass of solids can be determined by the use of the laboratory
balance. The volume of regularly shaped solids can be determined by
the dimensions and geometric formulae for volume. However, for
irregularly shaped objects, it is common to use the method of water
displacement. Since it is a law of physics that no two objects can
occupy the same space at the same time, a substance which is more
dense than water will sink in water and push aside (i.e. displace) its
own volume of water."
"Determination of Density":
Density of a sample = mass of sample / volume of sample.
If the sample displaces 1 liter of water when submerged, then its
volume is 1 liter or 1 dm^3 or 0.001 m^3 .
Then its density D is:
D = 6 kg / 0.001 m^3 = 6,000 kg/m^3
or if you prefer other units:
D = 6.0 kg/liter = 6.0 kg/dm^3
I hope that this helps you. Feel free to request for a clarification
if you need it.