2026 Units and MeasurementsSignificant figures in measured and derived quantities Medium Question 3 of 53 in Units and Measurements

Each side of a metallic cube of mass 5.580 kg is measured to be 9.0 cm. Keeping the significant figures in view, the density of the material of the cube can be best expressed as $X \times 10^3\ kg\,m^{-3}$, where the value of X is:

A 7.654
B 7.7
C 7.65
D 7.6

The answer is B.

Solution

Density $= \frac{mass}{volume} = \frac{5.580\ kg}{(9.0 \times 10^{-2})^3}$ $= 7.654 \times 10^3\ kg/m^3$ The side 9.0 cm has only 2 significant figures, so the result is rounded off to 2 significant figures: $7.7 \times 10^3$ $\Rightarrow X = 7.7$

Units and Measurements in past papers

53 questions from this chapter have appeared across 25 exam years.