Is your child ready to go 3-D? No, we're not talking about the newest round of three-dimensional movies and shows. This is all about geometry! Once he's mastered the basics, it's time to start finding the areas of 3-D shapes, like cubes. The six-sided cube isn't too difficult, because its surface area is made up of six squares with the same areas.

Ready for more three-dimensional shapes? Try finding the surface area of a rectangular prism.