Nonagon

A nonagon is a polygon with nine sides and nine angles. It is also known as a nine-sided polygon. The sum of the interior angles of a nonagon is 1260 degrees. Each interior angle of a regular nonagon measures 140 degrees.

Properties of a Nonagon

Number of Sides: 9
Number of Angles: 9
Sum of Interior Angles: 1260 degrees
Each Interior Angle (in a regular nonagon): 140 degrees
Each Exterior Angle: 40 degrees (since interior and exterior angles are supplementary)

Formula to Find Sum of Interior Angles

The formula to find the sum of the interior angles of a polygon is given by: (n-2) * 180, where n is the number of sides of the polygon. For a nonagon, the formula becomes: (9-2) * 180 = 7 * 180 = 1260 degrees.

Regular Nonagon vs. Irregular Nonagon

A regular nonagon has all its sides and angles equal in measure. An irregular nonagon has sides and/or angles with different measures.

Examples of Nonagon

Here are a few examples of nonagon in real life:

Stop sign: The red, octagonal shape of a stop sign is a real-world example of a nonagon.
Some gemstones and crystals are naturally nonagonal in shape.

Practice Problems

1. Calculate the measure of each interior angle of a regular nonagon.
2. Find the sum of the interior angles of an irregular nonagon with the following measures: 130°, 140°, 120°, 125°, 135°, 150°, 125°, 140°, 130°.
3. Draw a sketch of a nonagon and label its sides and angles.

◂Math Worksheets and Study Guides Fifth Grade. Order of Operations

The resources above cover the following skills:

Algebra (NCTM)

Use mathematical models to represent and understand quantitative relationships.

Model problem situations with objects and use representations such as graphs, tables, and equations to draw conclusions.

Connections to the Grade 5 Focal Points (NCTM)

Algebra: Students use patterns, models, and relationships as contexts for writing and solving simple equations and inequalities. They create graphs of simple equations. They explore prime and composite numbers and discover concepts related to the addition and subtraction of fractions as they use factors and multiples, including applications of common factors and common multiples. They develop an understanding of the order of operations and use it for all operations.