Perimeter with Geoboards
Students will be able to determine the perimeter of polygons.
- Ask students to think about what it means when a security guard “walks the perimeter” of a building.
- Call on students to hear their answers, and confirm that the perimeter is the outside of the building. In the example, the security guard is walking around the building to make sure that everything is safe.
- Explain that today’s lesson will be about how to determine the perimeter of shapes.
Explicit Instruction/Teacher modeling(10 minutes)
- Explain to students that the perimeter is the distance around a two-dimensional shape that has straight lines. It can be calculated by measuring the length of each side and adding them up. The length is how long one side of the shape is.
- Draw an example of a rectangle, and tell students that the lengths of the sides are 8 units, 8 units, 4 units, and 4 units. Be sure to explain that the longer sides have bigger lengths than the shorter sides. Point out that there are two sets of sides that are equal lengths in a rectangle.
- Model writing out an addition problem to find the sum of the lengths. Show that the shape has a perimeter of 24 units. Repeat this process with other shapes.
- Display a Geoboard and model how to use it. Wrap the rubberbands around the pegs to make different polygons. For example, create a square with a perimeter of 8 units. Show that each side is 2 units.
- Model this process with more shapes, explaining how to calculate the perimeter.
Guided Practice(15 minutes)
- Put students into partnerships and direct them to take out a whiteboard and a whiteboard marker. Give each pair a Geoboard and rubber bands.
- Instruct students to create shapes on the Geoboards based on the following questions:
- Create a triangle. The length of each side is 3 units. What is the perimeter?
- Create a square. The length of each side is 3 units. What is the perimeter?
- Create a triangle. The length of each side is 1 unit. What is the perimeter?
- Create a rectangle. The lengths of two of the sides are 3 units. The lengths of the other two sides are 2 units. What is the perimeter?
- Have students record their answers on a whiteboard. (Note: Some of these may need to be adjusted based on the size of the Geoboards.)
- Circulate and monitor partnerships as they create each shape and discuss how they determine the perimeter.
- Call on nonvolunteers to share the shapes they created, how they figured out how to make them, and how they calculated the perimeter.
Independent working time(10 minutes)
- Distribute a sheet of blank graph paper to each student.
- Display the following directions on the board:
- Create a square. The length of each side is 5 units. What is the perimeter?
- Create a triangle. The length of each side is 4 units. What is the perimeter?
- Create a rectangle. The lengths of two sides are 8 units. The lengths of the other two sides is 3 units. What is the perimeter?
- Direct students to complete the task on their sheet of blank graph paper. Instruct them to label the lengths of the sides and figure out the perimeter by adding up the lengths. They should show the addition problem on the paper.
- Provide students with a word wall or word bank that shows the different types of polygons (triangle, rectangle, square).
- Intentionally partner students based on academic needs to best support language learners.
- Teach a pre-lesson to review the different types of two-dimensional shapes and their characteristics. Use a graphic organizer for students to take notes, and allow them to reference it during this lesson.
- Give students graph paper with premade shapes on them, so they only have to focus on determining the lengths of sides that add up to the given perimeter.
- Draw an example of a Frayer Model Graphic Organizer on the board for students to use as a reference during the Exit Ticket.
- Give students an opportunity to complete the Perimeter Match worksheet on which they will explore how shapes can be different while having the same perimeter.
- Reword the problems for advanced students by only giving them the type of shape and the perimeter. Challenge them to determine the lengths of the sides.
- Provide tools for measuring and instruct advanced students to determine the perimeter of items and places in the school.
- Use the app called Geoboard, by the Math Learning Center to give students access to virtual Geoboards.
- Collect the Independent Practice students completed to determine levels of mastery with perimeter.
- Distribute a copy of the Frayer Model graphic organizer to each student, and explain each section. Choose a familiar term (e.g. addition) and model completing the graphic organizer.
- Instruct individuals to complete a Frayer Model Graphic Organizer for the word “Perimeter”.
Review and closing(2 minutes)
- Remind students that the perimeter is the distance around a two-dimensional shape. Ask students to think about what jobs use the concept of perimeter. (engineers, construction workers, interior designers)
- Call on students to share their ideas.