Lesson 3: Polygon Attributes

Day 2

Activity 3: Is It Regular or Irregular?

Materials: fine point dry-erase marker (kit), scissors, whiteboard (kit)
Ask your child to cut out all of the shapes on the "Sorting Polygons" sheet. Don't tell your child this yet, but some of these shapes are "regular" (all sides are the same length) and some are "irregular" (the sides are of varying lengths). While your child is cutting out the shapes, draw a line long-ways down the middle of a whiteboard to create two columns. Once all of the shapes are cut out, explain to your child that you are going to put them one-by-one into two different groups and that he should watch to see if he can figure out how you're grouping them.

Without saying the words "regular" and "irregular," begin by placing one of the regular shapes near the top of the left column on the whiteboard. Then place another regular shape right below it. Don't say anything at this point. Just let your child observe your work. Next, place an irregular shape near the top of the right column, again without saying anything. Place another irregular shape below it. Next, select another regular shape, and place it in the left column.

Now show a regular shape, and ask your child which column he thinks it should go in and why. He should want to put it in the left column with the other regular shapes, and he may note that all the regular shapes "look even" or "have the same sides." Pick up an irregular shape and ask him where it should go (the right column). Allow him to place the remaining shapes in the columns where he thinks they belong, and ask him to share why he's putting them where he is as he works. When he's finished, invite him to create names for each group of shapes that explain how the groups are different from each other. Point out that the shapes that have sides that are same length are called regular, and the shapes that have sides that are different lengths are called irregular. Write "regular" at the top of the left column and "irregular" at the top of the right column.
"Sorting Polygons" Answer Key

Activity 4: Creating Shapes

Materials: geoboard (kit), rubber bands (kit)
Your child will use either a geoboard and rubber bands or the geoboard tool at the following web link to create shapes based on the clues provided on the "Creating Shapes" sheet.
Web Link
  1. This shape is regular and has 3 sides. (triangle whose sides are the same length)
  2. This shape is irregular and has 4 angles. (a rectangle or other four-sided polygon whose sides are not all the same length)
  3. This shape is irregular and has 5 vertices. (pentagon whose sides are not all the same length)
  4. This shape is regular and has 8 angles. (octagon whose sides are the same length)
  5. This shape is irregular, has 4 vertices, and 2 sides that are the same length. (rectangle)