1)
The volume of object, V=15 mL.
The density of object, D= 3g/mL.
The mass of the object is,
[tex]\begin{gathered} \text{Mass}=\text{Volume}\times Density \\ M=V\times D \\ =15\text{ mL}\times3\text{ g/mL} \\ =45\text{ g} \end{gathered}[/tex]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,
[tex]\begin{gathered} \text{Volume}=\frac{\text{Mass}}{Density} \\ V=\frac{M}{D} \\ =\frac{2g}{4\text{ g/mL}} \\ =0.5\text{ mL} \end{gathered}[/tex]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,
[tex]\begin{gathered} D=\frac{M}{V} \\ =\frac{9\text{ g}}{12\text{ mL}} \\ =0.75\text{ g/mL} \end{gathered}[/tex]Therefore, the density of the object is 0.75 g/mL.
