# Assuming the earth to be a sphere of radius 6370 km,

Question:

Assuming the earth to be a sphere of radius 6370 km, how many square kilometers is the area of the land if three-fourths of the earth’s surface is covered by water?

Solution:

$3 / 4^{\text {th }}$ of earth surface is covered by water

Therefore $1 / 4^{\text {th }}$ of earth surface is covered by land

Therefore Surface area covered by land $=1 / 4 \times 4 \pi r^{2}$

$=1 / 4 \times 4 \times 22 / 7 \times(6370)^{2}$

$=127527400 \mathrm{~km}^{2}$