Guided Lessons

# Finding Perimeter

In this lesson, students will find the perimeter of figures using cheese crackers. Next, they'll design a floor plan for their cheese cracker dream house, to help them practise and retain the formula for finding perimeter.

No standards associated with this content.

No standards associated with this content.

No standards associated with this content.

No standards associated with this content.

No standards associated with this content.

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Students will be able to find the perimeter of a given geometric figure.

(10 minutes)
1. Play the video Perimeter, by maths Antics, for the class to introduce the concept of perimeter.
2. Once the video is complete, ask for a volunteer to tell you the definition of perimeter.
3. Write the definition on the board.
4. Draw a few figures on the board, along with the lengths of their sides.
5. Challenge students to find the perimeter of the geometrical figures you’ve drawn.
6. Each time a student answers, correctly or incorrectly, explain the reasoning behind each figure’s perimeter.
(20 minutes)
• Start by showing your students how to use unit squares to count the perimeter units of a figure. For example, find an object in the classroom, such as a book, to measure.
• Using the cheese crackers (or the unit of your choice), model how students would find the perimeter of the book by placing crackers side-by-side, all around the book.
• Write the unit measurements on the board, and then ask the class to find the perimeter.
• For example, if the object you measured is 3 crackers on one side, by 7 crackers on another side, the perimeter (total) would be 3 + 3 + 7 + 7, or 20 crackers.
(20 minutes)
• Once you’ve finished modeling finding the perimeter, tell students to make a 3x5 array (rectangle) with the cheese crackers.
• As the class creates the rectangle, ask students to find the perimeter when they’re done, and record the perimeter in their maths journals.
• Once the class is done, demonstrate how to draw a 3x5 rectangle, and how to find the perimeter, using a projector or document camera.
• Have students create a 2x10 rectangle this time, and repeat the process. Walk around the class to support students, as they need it.
• Pass out copies of the Find the Perimeter worksheet (see attached).
• Model two of the problems for the class on the board, with a document camera or with a projector.
(20 minutes)
• Have students finish the rest of the Find the Perimeter worksheet independently. If students get stuck, have them raise their hand for your assistance.
• As students complete the worksheet, check their answers.
• Students who successfully complete the worksheet should move on to their application project, creating a Dream House.
• Tell the class that each person will create a floor plan for their dream house, using cheese crackers to design and measure their layout.
• Once they’ve created a floor plan, have students record it in their maths journal. The maths journal should include a drawing of the floor plan, and the perimeter.
• Enrichment:Students who need more of a challenge can build multiple floor plans (for a multi-level dream house) during independent working time. You can also have these students find the area in addition to the perimeter.
• Support:Arrange students who are struggling into a small group to work with you. Complete the Find the Perimeter worksheet as a group, using cheese crackers as manipulatives.
(5 minutes)
• Review your students’ worksheets and dream house floor plans to assess their understanding of perimeter.
(10 minutes)
• Students will complete “Perimeter Four Square Review” as their journal reflection.