##### Center Focus

# Shapes and Angles

- Have your students figure out the sum of the angles of a rectangle. Give them this reproducible that explains why the angles of a four-sided figure will always add up to 360 degrees.
- Based on this reasoning, have your students figure out the sum of angles of other shapes, i.e. pentagon, hexagon, dodecahedron.
- These shapes are all regular shapes--the interior angles are equal and the lengths of the sides are equal. As your students experiment with figures that have unequal angles/sides, they will realize that all four-sided figures have interior angles that sum to 360 degrees. Likewise, all eight-sided figures have interior angles that add up to 1080 degrees.
- In order to help your students prove this, have them measure the angles of a 5-pointed star using a protractor. Download a five-pointed star here. They should add up the angles (10 of them); the sum will be 1440. You may want to have them continue doing this with other shapes to further their understanding.
- This download should be helpful for this activity. It is a list of shapes, from 4-sided to 12-sided, and the sum of their angles.