### Context for this Lesson

TOPIC: Geometry skills and applications

GRADES: 2 or 3

FOCUS QUESTIONS: What are the differences between basic shapes? How do you find the area and perimeter of basic shapes? What are real-life applications of shapes?

MATERIALS:

- Blueprint handouts
- String
- Character Glasses (or other “costume” piece)

TEKS Grade 2: 111.4(b)(8) Geometry and measurement. The student applies mathematical process standards to analyze attributes of two-dimensional shapes and three-dimensional solids to develop generalizations about their properties. The student is expected to: (A) create two-dimensional shapes based on given attributes, including number of sides and vertices; Grade 3: 111.5 (b) (6): Geometry and measurement. The student applies mathematical process standards to analyze attributes of two-dimensional geometric figures to develop generalizations about their properties. The student is expected to: (B) determine the perimeter of a polygon or a missing length when given perimeter and remaining side lengths in problems;

ENGAGE: STRING SHAPES

Students begin in a circle. The instructor introduces the length of yarn and students gather around and pick up yarn, holding it at waist level. Students are instructed to work together to make a basic shape: a circle.

After they have successfully accomplished this task, increase the difficulty by introducing harder shapes: triangles, squares, rectangles or even polygons. Once the players have successfully created a shape or two, ask them to refrain from talking and communicate silently with their group to create the shapes. The players can’t let go of the string at any time and must use every player to make the shape given.

After they have successfully completed this, ask students to create a triangle with 5 hands on each side. Ask: if we are thinking of hands like a unit of measurement, what would our perimeter be? Then ask them to create a rectangle with sides of 4 and 6 hands. Work together to decide the perimeter. Once they’ve completed this task, invite them to take their seats.

TEACHER IN ROLE/MANTLE OF THE EXPERT

Teacher: In a moment, we are going to use our knowledge of these shapes and how to find a perimeter to help someone who is having a problem. When I put these glasses on I am going to become a character who needs your help. I’m going to invite you to pretend to be workers at a fence building company, Fences R Us. Are you ready? We’ll begin on the count of 3. You can count with me, 3-2-1!

(Put on glasses and “transform” into character.)

PENELOPE: "Hello! I am so glad that you were able to fit me in your schedule. I know you are such busy fence builders! My name is Penelope and I have a really important project I need your help with. My dog, Sparky, keeps running away. I put him outside and POOF! he’s gone. I think I need a really good fence to keep him in my yard. But, here’s the thing. I found this blueprint, or layout of my house and yard, and it’s really old. Some of the numbers are even missing! But it does say the perimeter of the yard. I know that you all are experts in finding perimeter, since you build fences around the perimeter of yards. So, if you could help me figure out the missing numbers, I would really appreciate it. Then, I can order all the materials to make my fence. Do you think you can help me?"

(Pass out blueprints of house/yard. Each group gets assigned a shape to find the missing side.)

"Alright, what did you come up with? Ask the students to show their work. What was the math problem that you wrote to find the answer? Oh, thank you so much! I need help with one more thing! I need to know how much fencing to order for the whole yard. So, in your groups can you find the perimeter of the whole yard? How would you do that? I don’t even know where to start!"

(Share out perimeters. Double check work together.)

"Thank you so, so much! I am so happy I was able to get an appointment with such smart fence builders. I just need one last piece of advice. What do you think I should build this fence out of? Those are all great ideas, thank you! I have to go get started. Sparky will never be able to run away again! Goodbye!"

(De-role teacher and students.)

Describe: Who did you just meet? What was her problem?

Analyze: How did you help Penelope solve her problem?

Relate: Can you think of other times around your house or at school when it would be important to know the perimeter of shapes?