Perimeter of Play
Students will be able to apply their understanding of perimeter to a real-world scenario.
- Display the Summer Coloring Page, or something else of interest to your students, and ask them how much fencing they'll need to enclose this backyard.
- Gather information about what they know about perimeter in real-world situations by asking them questions. For example, "What would the fence have to look like for us to measure the perimeter? What measurement would we use for a large backyard? Would the backyard have the same perimeter as a football field?"
- Ask a student to read the student objective and define perimeter as the distance around a two-dimensional shape that has straight lines.
- Have students brainstorm in pairs other realistic scenarios where it would be helpful to know the perimeter (e.g., fencing, framing a picture, and construction).
- Tell students that perimeter is useful for many things, especially when you want to surround an object with something, or make sure you have enough space to fit an object. Explain that when someone wants to build a gate around their yard or their garden, they will need to know the perimeter to decide how much fencing they'll need.
Explicit Instruction/Teacher modeling(7 minutes)
- Tell students they can find the perimeter of an object by adding up all the sides or using the equation 2L + 2W. Write 10 feet x 9 feet on the board and draw the rectangle based on that dimension, highlighting that there are two 10 ft sides and two 9 ft sides.
- Show students how the dimension 10 ft x 9 ft can translate to 2(10 ft) + 2(9 ft) and write the equation 10 ft + 10 ft+ 9 ft + 9 ft next to the multiplication equation. Model using the perimeter equation to find the perimeter of the rectangle and check your answer by adding up all the sides of the rectangle.
- Create a 10 ft by 9 ft rectangle in the classroom by walking 10 steps for two sides and 9 steps for the other two sides. Emphasize that this is just an estimation of the size and have students focus on this visual when discussing the amount of space within the rectangle. Ask students to brainstorm things that could fit in a 10 ft x 9 ft rectangle (e.g., bedroom, ping-pong table, table for board games).
Guided Practice(15 minutes)
- Model using the formula to draw 10 ft x 9 ft on the graph paper. Choose students to share their partner brainstorm ideas aloud and have students put their thumbs up if they agree and thumbs down if they don't. Write the object or activity that the students agree would fit in the middle of the drawn rectangles on the graph paper.
- Distribute the graph paper and pair students up. Have them graph 15 ft by 12 ft and write objects or things they could do within that space (e.g., play video games on the couch). Allow a few students to present their graphed example and tell what will fit into the rectangle and ask a volunteer to explain the process of graphing the rectangle based on the dimensions.
- Write 16 ft + ____ + 16 ft + ____ = 50 ft on the board. Tell students this is the perimeter of a rectangle, and ask them to fill in the blanks. Instruct them to use the back of their graph paper to show their work. Walk around and monitor while they are working to see who is able to find the missing sides and perimeter (16 ft + 9 ft + 16 ft + 9 ft = 50 ft).
- Have a student explain that they found the missing sides by subtracting the known sides from the perimeter and dividing the difference by 2 to find the measurement of the other two equal sides.
- Ask for volunteers to share their answers and for other volunteers to add on to the student’s response. Assist them with their sharing by asking follow-up questions: "What made you choose that number? Could you have chosen another number?"
Independent working time(15 minutes)
- Distribute the worksheet Perimeter: Perfect Carnival and review the sections. Relate their graph paper dimension drawing and the missing numbers within the equations they've already done to what they will do in the worksheet.
- Ask a student to reword the directions. Tell students they can use the back of their graph paper or the worksheet for their work in the first section.
- Allow volunteers to share their ideal carnival and explain what why they chose each activity.
- Allow students to walk out the dimensions of the rectangles to determine what activity would fit in those dimensions.
- Provide posters on the word wall for the words "perimeter," "rectangles," and "perimeter equation."
- Provide visuals of the activities in the Perimeter: Perfect Carnival worksheet to build their vocabulary and help them see how much space the activity typically takes.
- Distribute additional graph paper and allow students to recreate the worksheet with more challenging dimensions and different activities. Their carnival will have the space of a football field to allow for more activities.
- Distribute an index card and ask students to write why they think finding the perimeter may be important in the real world, and how they can use perimeter in the future.
- Provide the following sentence starters if necessary:
- Finding the perimeter before projects is important because…
- I can use perimeter when I…
- Perimeter is useful when…
Review and closing(5 minutes)
- Ask students to share the hardest or easiest part of planning their perfect carnival.
- Help students add detail to their explanations by asking questions: "Were there activities you wanted to add but could not? If so, why couldn't you add them? How did you choose between one activity over another?"