The mass of a piece of paper is 0.02 g and the mass of a solid substance and the piece of paper is 20.036 g. If the volume of the solid is 2.16 cm³, calculate the density of the substance up to proper number of significant digits.

Mass of piece of paper - 0.02 g
Mass of solid substance and piece of paper - 20.036 g
.'. Mass of solid substance : 20.036

$\frac{0.020}{20.016}$

or :20.02 (up to second decimal place)
Volume of solid - 2.16 cm³

$\text{ Density }=\frac{\text{ Mass }}{\text{ Volume }}=\frac{20.02}{2.16}=9.268$

Since 2.16 has 3 significant figures, the answer should also contain 3 significant figures.
.'. Density up to proper number of significant figures : 9.27 glcm³.'