A sphere is a perfectly symmetrical 3-dimensional object:

Its dimensions can be characterized by a single parameter: its radius* r*. Every point on the sphere’s surface is at a distance of *r* from the sphere’s *center*.

If you cut a sphere in half, you obtain a hemisphere:

Note that a hemisphere has a curved surface area as well as a (circular) flat surface area.

• Download Mensuration and Solids Worksheets