How to Solve for Radius in Excel. The radius of a circle or a sphere is the distance between the center and the edge. The radius can be used to calculate a circle's diameter, area and circumference.

Calculate the circumference of the Earth using this equation: Circumference = 360 x distance between your city and the equator / angle of shadow that you measured What value do you get?

This KS2 maths article explains how to measure the radius, circumference and diameter of a circle.

The circumference of a circle is its outside edge, and is the same distance from the centre at every point along its length. This distance is called the radius.