Answer
$5.5 \times 10^{3} kg/m^{3}$
Work Step by Step
Mass of earth $= 5.98 \times 10^{24} kg $
Radius of earth $= 6400 km = 6.4 \times 10^{6} m$
Volume $= \frac{4}{3} \times \frac{22}{7} \times radius^{3}=1.1 \times 10^{21} m^{3} $
Thus, Density $ = \frac{5.98 \times 10^{24}}{1.1\times 10^{21}}=5.5\times 10^{3} kg/m^{3}$