Grade 5:
Here is the way (also called a FORMULA) to find the interior angles of any regular polygon:

Step 1: Number of Sides - 2
Step 2: Multiply your answer from step 1 by 180
Step 3: Divide your answer from step 2 by the number of sides of your polygon.

Let's see if it work!

For a regular quadrilateral (square):

Step 1: 4 - 2 = 2
Step 2: 180 x 2 = 360
Step 3: 360 ÷ 4 = 90 Which is correct!

Do it for all the other polygons. Remember..... the greater the number of sides of your regular polygon, the larger the angle size.

Regular polygons..... equal sides, equal angles AND the number of sides = the number of lines of symmetry.

This will be VERY helpful for your Geometry test tomorrow.