What is the mass density of a rock of mass 300 g that has an apparent mass of 200 g in water?
The density is 3.00 grams/ ml
The rock weighs 100 grams less in water than it does in air
The density of water is
so 100 gram difference means 100 ml of water were displaced.
so the volume of the rock is 100 ml.
Density = Mass / Volume.