About 70% of earth is covered in water, making 30% of earth potentially habitable by humans. Earth can be modeled as a sphere with diameter 12, 700 km. There are 7.1 billion people in the world. What is the population density of potentially habitable earth?

B - About 50 people per km^2

Explanation:

I took the khan test and got this question correct

The population density is 47 people/km^2 ...

Step 1. Calculate the surface area of Earth.

d = 12 700 km; r = 6350 km

A = 4πr^2 = 4π * (6350 km) ^2 = 5.067 * 10^8 km^2

Step 2. Calculate the habitable surface area.

Habitable area = 5.067 * 10^8 km^2 total * (30 km^2 habitable/100 km^2 total) = 1.520 * 10^8 km^2 habitable

Step 3. Calculate the population density

Population density = 7.1 * 10^9 people/1.520 * 10^8 km^2 = 47 people/km^2