Answer:
If we were to take a cross-section of our planet on the equator we would get a circle. So, basically, the circumference of this circle is the distance one would have to travel to go around the earth. The formula for the circumference of the circle is 2 x r x pi. Radius of the Earth is r, and pi is approximately 3.1415. So, the circumference is 2 x 6370 x 3.1415, which equals to 40 029 km, or approximately 40 thousand kilometers.
