Exploring Perimeter Basics

Overview

This 30-minute lesson introduces Grade 4 students to the concept of perimeter, aligning with the Ontario Mathematics Curriculum (Grades 3 and 4) expectations. Using hands-on, interactive activities, students will develop an intuitive and practical understanding of perimeter, setting the foundation for further measurement and geometry studies.

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Curriculum Connections

Ontario Mathematics Curriculum (Grades 3-4), Geometry and Spatial Sense

• Understanding and Applying Geometric Properties and Relations:
  Geometry and Spatial Sense – G3.1: Measure and calculate the perimeter of polygons, including squares and rectangles, using concrete materials and drawings.

• Measurement:
  Measurement – M2.2: Estimate, measure, and record perimeter of objects, using standard units (cm, m) and non-standard units.

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Learning Goals

• Define perimeter as the distance around a two-dimensional shape.
• Measure the perimeter of simple polygons (rectangles, squares) using non-standard and standard units.
• Connect the concept of perimeter to everyday contexts.

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Success Criteria

Students will be able to:

• Explain in their own words what perimeter means.
• Measure perimeter using their hand spans (non-standard units) and rulers (standard units).
• Calculate the perimeter by adding the lengths of all sides of a given shape.
• Show understanding through a simple drawing and accurate measurement.

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Materials Needed

• Rulers (cm) – 1 per student
• String or yarn (about 30 cm pieces) – several sets (shared)
• Handout with pre-drawn shapes (squares, rectangles, other polygons) - 1 per student
• Whiteboard & markers
• Tape measure or meter sticks (for teacher demonstration)
• Sticky notes
• Chart paper or interactive whiteboard

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Lesson Flow

1. Engage (5 minutes)

• Begin by asking: “Have you ever walked around a playground or a garden? How do you think we could know how far we walked around it?”
• Introduce the word perimeter and define it simply: "The perimeter is the distance all around a shape."
• Use a large shape drawn on the board (e.g., rectangle) and invite volunteers to come up and "walk" the edges with their finger while the class counts the steps aloud in non-standard units (e.g., hand spans).
• Connect back: "So, measuring the perimeter means finding this total distance around any shape."

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2. Explore (10 minutes)

• Distribute handouts with polygons and rulers.
• Model measuring perimeter of a rectangle first: measure each side length, then add all four side lengths together. Record this on the board, emphasising addition of side lengths.
• Introduce using non-standard units: hand spans or string pieces. Ask students to estimate and measure perimeters around printed shapes using these units first, then try rulers to compare.
• Students work in pairs to measure and calculate the perimeters of different shapes on their handouts. Provide support and scaffold as needed.

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3. Explain (7 minutes)

• Regroup and discuss: “How did we find the perimeter of the shapes?”
• Write an example on the board:
  Perimeter = side 1 + side 2 + side 3 + side 4
• Highlight that all sides need to be measured and added to find the perimeter.
• Clarify vocabulary: side, edge, polygon, unit of measure.
• Use chart paper or interactive whiteboard to create a Perimeter Steps Chart, summarizing:
  1. Identify the shape’s sides
  2. Measure each side
  3. Add the lengths together
  4. State your answer with units

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4. Elaborate (5 minutes)

• Present a real-world challenge: "Imagine you want to put a fence around a garden shaped like a rectangle, 5 m long and 3 m wide. How much fencing do you need?"
• Students discuss in pairs, then share ideas.
• Teacher helps calculate the perimeter: 5 + 3 + 5 + 3 = 16 m.
• Reinforce the practical use of perimeter in daily life.

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5. Evaluate and Consolidate (3 minutes)

• Quick ‘exit ticket’: Each student writes on a sticky note one sentence explaining “What is perimeter?” and one example of an object they could measure the perimeter of.
• Collect notes to assess understanding.

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Differentiation

• For students needing support:

  • Provide shapes with clear labelled side lengths to focus on addition.
  • Use larger, simpler shapes.
  • Verbal prompts during pair work.

• For extending learners:

  • Challenge to find perimeter of irregular polygons.
  • Explore perimeter using decimals or fractional units.
  • Predict how changing side length affects perimeter and justify.

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Teacher Reflection

• Were students able to explain perimeter in their own words?
• Did students demonstrate ability to measure and add side lengths correctly?
• Were students able to connect perimeter to real-world contexts?
• What adjustments might improve engagement or understanding for the next lesson?

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Note: This lesson is designed to engage multiple learning styles through tactile measurement, visual representation, and verbal explanation, fulfilling key elements of the Ontario curriculum framework for mathematics in Grades 3 and 4 while fostering curiosity and practical application.