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. Likewise, a sphere's volume is ...

A sphere is a perfectly round solid figure. All points on the surface of the shape are the same distance away from the centre – we call this distance the radius. The formula for the volume and surface ...

For ages 12 and older. How many grains of sand would it take to fill the universe? This is a problem that the Greek mathematician Archimedes tried to solve in the third century B.C. In this activity, ...