The volume of a piece of metal of a mass 6 gram is 15cm3. What is the density of the metal piece?

0.4 g/cm^3

Explanation:

The density of an object can be found using the following formula.

d= m/v

where m is the mass and v is the volume.

The mass of the metal is 6 grams and the volume is 15 centimeters^3

m=6 g

v= 15 cm^3

Substitute these into the formula.

d= 6 g/ 15 cm^3

Divide 6 g by 15 cm^3 (6/15=0.4)

d= 0.4 g/ cm^3

The density of the metal is 0.4 grams per cubic centimeter.

Density = (mass) / (volume)

Density = (6 g) / (15 cm³)

Density = (6/15) (g/cm³)

Density = 0.4 g/cm³

This 'metal' has less than half the density of water, and it floats on water !  It cannot be of Earthly origin, and must have been dropped here by aliens.

Either that, or else the metal has been hammered and stretched and beaten out and shaped so that it has an artificially large volume ... something like the way sailing ships are made out of thick plates of steel.