Question

if you cut the marble into two equal pieces, what will be the density , mass and volume of one of those pieces.

Answer 1

density is the same.
Mass is 1/2 of the original mass.
Volume is 1/2 of the original volume.
Since density = mass/volume, taking 1/2 the mass and 1/2 the volume acts to cancel so the fraction of mass/volume doesn't change.