Question:
The diameter of the moon is approximately one-fourth of the diameter of the earth. Find the ratio of their surface areas.
Solution:
Let the diameter of the earth be d
Then,
Diameter of moon will be d/4
Radius of earth = d/2
Radius of moon $=\frac{\frac{\mathrm{d}}{2}}{4}=\frac{\mathrm{d}}{8}$
Surface area of moon $=4 \pi(\mathrm{d} / 8)^{2}$
Surface area of earth $=4 \pi(d / 2)^{2}$
Required Ratio $=\frac{4 \pi\left(\frac{\mathrm{d}}{8}\right)^{2}}{4 \pi\left(\frac{\mathrm{d}}{2}\right)^{2}}$
$=\frac{4}{64}=\frac{1}{16}$
Thus the required ratio of the surface areas is 1/16