Geometry, Symmetry, Concept of Symmetry for Primary 3

Class: Primary 3
Term: 3rd Term
Week: 5
Age: 8 years
Duration: 45 minutes
Subject: Mathematics
Curriculum Theme: Geometry
Previous Lesson: Time and Calendar, Reading Days of the Week.
Topic: Geometry – Symmetry
Subject Matter: Concept of symmetry, Identifying symmetrical shapes, Identifying lines of symmetry in various objects, Folding various plane shapes along their lines of symmetry, Finding the number of lines of symmetry, Word problems on lines of symmetry.

Specific Objectives

By the end of the lesson, pupils should be able to:

Cognitive Domain:

• Define symmetry.
• Identify symmetrical objects and shapes.
• Identify lines of symmetry in various objects and shapes.
• Find the number of lines of symmetry for common shapes.
• Solve simple word problems related to lines of symmetry.

Affective Domain:

• Appreciate the presence of symmetry in nature and everyday objects.
• Show carefulness when folding shapes to find lines of symmetry.
• Demonstrate interest in learning about geometric properties.

Psychomotor Domain:

• Fold various plane shapes accurately along their lines of symmetry.
• Draw lines of symmetry on given symmetrical shapes.
• Cut out symmetrical shapes from paper.

Social Domain:

• Work collaboratively with peers to identify symmetrical shapes.
• Share their findings and observations about symmetry with the class.

Reference Materials

The following resources were used in planning this lesson:

• 9 Years Basic Education Curriculum for Primary 3 Mathematics
• State Unified Scheme of Work
• New General Mathematics for Primary 3
• Teacher-made cut-out shapes (square, rectangle, circle, triangle)

Instructional Materials

The teacher will teach this lesson with the aid of:

• Cut-out paper shapes (square, rectangle, circle, equilateral triangle)
• Real-life symmetrical objects (e.g., a leaf, a butterfly picture, a chair)
• Ruler and pencil
• Whiteboard and markers

Rationale for the Lesson

This lesson helps pupils understand the concept of symmetry, which is fundamental in geometry and observed widely in nature and man-made objects. Learning about symmetry develops pupils’ spatial reasoning and problem-solving skills, enabling them to better appreciate and analyze patterns in their environment.

Prerequisite/Previous Knowledge

Pupils have prior knowledge of basic plane shapes such as squares, rectangles, triangles, and circles.

Lesson Content/Board Summary

Symmetry

Concept of Symmetry

Symmetry means that a shape or object can be divided into two identical halves that mirror each other. If you fold a symmetrical shape along its middle, both halves will match exactly.

Symmetrical Shapes

Symmetrical shapes are shapes that can be divided into two matching halves.
The following are examples of symmetrical shapes:

• Square
• Rectangle
• Circle
• Equilateral Triangle
• A heart shape
• A butterfly
• A human face

Line of Symmetry

A line of symmetry is an imaginary line that divides a symmetrical shape or object into two identical mirror images. It is the fold line that makes both halves match perfectly.

Folding Shapes Along Their Lines of Symmetry

To find a line of symmetry, you can fold a paper shape. If the two halves match exactly, the fold line is a line of symmetry.

Number of Lines of Symmetry

Different shapes have different numbers of lines of symmetry.

• Square: A square has 4 lines of symmetry. (Two diagonal, two horizontal/vertical)
• Rectangle: A rectangle has 2 lines of symmetry. (One horizontal, one vertical)
• Equilateral Triangle: An equilateral triangle has 3 lines of symmetry.
• Circle: A circle has an infinite number of lines of symmetry. (Any line passing through its center is a line of symmetry)
• Isosceles Triangle: An isosceles triangle has 1 line of symmetry.

Word Problem on Lines of Symmetry

Question: A butterfly has wings that are identical on both sides. How many lines of symmetry does a butterfly typically have?

Solution: A butterfly typically has 1 line of symmetry, which runs down the middle of its body, dividing it into two matching halves.

Teaching Methods/Instructional Techniques

Discussion, Lecture, Demonstration, Question and Answer, Visual Aids

Instructional Procedures

Lesson: Geometry – Symmetry

Step 1: Introduction

Time: 5 minutes
Teaching Skill: Set Induction
Teacher’s Activity: The teacher greets the pupils and reviews the previous lesson on basic plane shapes. The teacher then shows pupils pictures of a butterfly, a leaf, and a chair, asking them what they notice about their appearance.
Pupils’ Activity: Pupils respond to questions and observe the objects shown by the teacher.
Learning Point: Pupils recall previous knowledge and are introduced to the concept of symmetry.

Step 2: Concept of Symmetry

Time: 8 minutes
Teaching Skill: Explanation/Demonstration
Teacher’s Activity: The teacher explains the concept of symmetry using simple language and demonstrates with a cut-out heart shape, folding it to show that both halves match. The teacher explains that a shape is symmetrical if it can be divided into two identical halves.
Pupils’ Activity: Pupils listen attentively and observe the teacher’s demonstration.
Learning Point: Pupils understand the definition of symmetry.

Step 3: Identifying Symmetrical Shapes

Time: 8 minutes
Teaching Skill: Activity/Identification
Teacher’s Activity: The teacher provides pupils with various cut-out shapes (square, rectangle, circle, a regular pentagon, and an irregular shape). The teacher asks pupils to identify which of these shapes are symmetrical by trying to fold them.
Pupils’ Activity: Pupils individually or in pairs attempt to fold the shapes and identify the symmetrical ones.
Learning Point: Pupils can identify symmetrical shapes through practical activity.

Step 4: Identifying Lines of Symmetry

Time: 8 minutes
Teaching Skill: Demonstration/Practice
Teacher’s Activity: The teacher explains what a line of symmetry is. Using a square cut-out, the teacher demonstrates how to fold it along its lines of symmetry, showing that the fold line is the line of symmetry. The teacher then guides pupils to do the same with their square and rectangle cut-outs.
Pupils’ Activity: Pupils practice folding their cut-out shapes to find and identify the lines of symmetry.
Learning Point: Pupils can identify and understand the meaning of a line of symmetry.

Step 5: Finding the Number of Lines of Symmetry

Time: 8 minutes
Teaching Skill: Guided Practice
Teacher’s Activity: The teacher leads a discussion on how many lines of symmetry different shapes have. Using the cut-outs, the teacher helps pupils count the lines of symmetry for a square (4), rectangle (2), equilateral triangle (3), and explains that a circle has many lines of symmetry.
Pupils’ Activity: Pupils count the lines of symmetry on their shapes and note down the numbers for each.
Learning Point: Pupils can determine the number of lines of symmetry for common shapes.

Step 6: Word Problems on Lines of Symmetry

Time: 4 minutes
Teaching Skill: Problem Solving
Teacher’s Activity: The teacher presents a simple word problem on the board related to symmetry, such as “A table has a rectangular top. How many lines of symmetry does the top of the table have?” and guides pupils through solving it.
Pupils’ Activity: Pupils attempt to solve the word problem and share their answers.
Learning Point: Pupils apply their knowledge of symmetry to solve simple real-world problems.

Step 7: Evaluation/Review

Time: 5 minutes
Teaching Skill: Questioning/Assessment
Teacher’s Activity: The teacher evaluates the learning by asking the following questions:

1. What is symmetry?
2. Give two examples of symmetrical shapes.
3. How many lines of symmetry does a square have?
4. How many lines of symmetry does a rectangle have?

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 2 minutes
Teaching Skill: Summarization
Teacher’s Activity: The teacher summarizes the key points of the lesson, reiterating the definition of symmetry, symmetrical shapes, and lines of symmetry. The teacher then gives pupils homework: to draw two symmetrical objects and their lines of symmetry.
Pupils’ Activity: Pupils listen to the summary and copy down the homework.
Learning Point: Pupils review the main concepts of the lesson.

Home Task: Solve three new exercises on Geometry – Symmetry. Show each step and check each answer.

Lesson Keywords

• Symmetry – When a shape or object can be divided into two identical halves that mirror each other.
• Symmetrical Shape – A shape that can be divided into two matching halves.
• Line of Symmetry – An imaginary line that divides a symmetrical shape into two identical mirror images.

Differentiation

For pupils who need extra support, the teacher will provide more pre-cut shapes and guide them individually through the folding activities. For advanced learners, the teacher will challenge them to find lines of symmetry in more complex shapes or objects, such as a regular hexagon or a letter of the alphabet.

Note for teachers using this lesson plan

Encourage practical activities during the lesson. Allow pupils to handle and fold shapes themselves to grasp the concept of symmetry and lines of symmetry. Use real-life examples to make the lesson relatable and engaging for the pupils.