Mr. Mason wrote: Sorry to be getting this in the AM but in a nutshell: Density = mass divided by volume.
So with the water:
Mass of the water and graduate minus the mass of the graduate equals the mass of the water and the volume equals 40mL.
(Mass of the water and graduate minus the mass of the graduate)g/40mL=?g/mL
With the rock:
Mass equals whatever reading you had on the balance and the volume equals the amount of water displaced when you submerged it (how much did the water go up?).
(Your reading on the balance)g/(How much the water went up)mL = ?g/mL