The Earth's surface area is approximately 5.1 * 10^8 km^2 (2 s.f.) and its population is 7.6 * 10^9 (2 s.f.). Population density is the number of people per square kilometre. Determine the population density of the Earth assuming all the the surface is land habitable by humans.
About 30% of the Earth's surface is land, including Antarctica. Determine the population density of the Earth assuming that all the land is habitable, but not the oceans.
[7.6 x 10^9] / [5.1 x 10^8] =~15 people per km^2 - human population density.
30% x [5.1 x 10^8] =1.53 x 10^8 Km^2 - the surface area of all the land.
[7.6 x 10^9] / [1.53 x 10^8] =~ 50 people per km^2 on all habitable land.