Elementary Geometry: Introducing the Rhombus and Other Polygons

Teaching Your Child About Polygons

Polygon Basics

A polygon is a two-dimensional shape with at least three straight sides and a corresponding number of angles. Your child will learn about many different polygons, including triangles (polygons with three sides), quadrilaterals (four sides), pentagons (five sides) and octagons (eight sides). Your child will also learn to identify different kinds of quadrilaterals, like the square, the rectangle, the parallelogram and the rhombus.

A rhombus is a four-sided polygon with these three characteristics: all sides are the same length, opposite angles are congruent and opposite sides are parallel. Rhombuses form the traditional diamond shape; for example, the bases on a baseball diamond are arranged in the shape of a rhombus.

A parallelogram has the same characteristics as a rhombus, except that it does not need to have four equal sides. Instead, it has opposite sides of equal length. Rectangles are very much like parallelograms, but they have four right angles; parallelograms have two sets of congruent angles. Squares have all of the characteristics of rectangles, but they also have four equal sides.

Fun Activities with Polygons

One hands-on activity is to have your child point out different kinds of polygons in the real world. No matter where you live, there are polygons all over your home, your car, the grocery store and anywhere else that you might take your child. You can ask him or her to find a certain number of objects with a given shape, or you can point out specific objects and ask what shapes they are.

Another fun activity you can use to engage your child in geometry is to give him or her a long piece of yarn. Then, ask your student to place it on a table and use it to create the outline of different shapes. You can also give him or her a second piece of yarn, which can be used to divide the original shape into smaller shapes. For example, it could be used to divide a rectangle into two squares or a parallelogram into two rhombuses.

Helpful Online Resources

The Internet can be a great place to find elementary geometry resources. Whether you're looking for free content or are willing to pay, you'll find worksheets, printables, quizzes, games and activities that can help your child.