The equatorial radius of the earth is 6378 km. Find the length of the earth’s equator.

We know the equatorial radius of the earth – it is equal to 6378 km. We need to find the length of the equator. The shape of the planet Earth is a sphere, and every section of a sphere by a plane is a circle.
So to find the length of the equator, we will use the formula for finding the length of a circle.
Let’s remember her:
With a known radius r, the formula for the circumference of a circle will look like this:
l = 2пr
We substitute the value of the equatorial radius of the earth in the formula for finding, in our case, the length of the equator and calculate:
l = 2 * 3.14 * 6378 = 40053.84 km.
Answer: 40,053.84 km.