1)
The volume of object, V=15 mL.
The density of object, D= 3g/mL.
The mass of the object is,
Therefore, the mass of the object is 45 g.
2)
Density, D=4 g/mL, Mass, M=2 g.
The volume of the object is,
Therefore, the volume of the object is 0.5 mL.
3)
Mass, M=9 g, Volume, V=12 mL.
The density of the object is,
Therefore, the density of the object is 0.75 g/mL.