Class: Primary 4
Term: 3rd Term
Week: 5
Age: 9 years
Duration: 45 minutes
Subject: General Mathematics
Curriculum Theme: Geometry
Previous Lesson: Capacity, Multiplication, Division and Word Problems in Litres.
Topic: PLANE SHAPES
Subject Matter: Identifying shapes with symmetry and non-symmetry, locating lines of symmetry of plane shapes, properties of rectangles and squares, constructing plane shapes to show symmetry lines, quantitative aptitude on plane shapes and symmetry.

Specific Objectives

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

Cognitive Domain:

Identify shapes with lines of symmetry and shapes without symmetry lines.
Locate the line(s) of symmetry of given plane shapes.
State the properties of rectangles and squares.
Solve quantitative aptitude problems on plane shapes and symmetry.

Affective Domain:

Appreciate the concept of symmetry in nature and everyday objects.
Show interest in exploring different types of plane shapes.

Psychomotor Domain:

Fold and cut plane shapes to find line(s) of symmetry.
Construct plane shapes and show their lines of symmetry.

Work cooperatively with peers to identify and construct symmetrical shapes.

Reference Materials

The following resources were used in planning this lesson:

9 Years Basic Education Curriculum
State Unified Scheme of Work
New General Mathematics for Primary 4

Instructional Materials

The teacher will teach this lesson with the aid of:

Cut-out paper shapes (square, rectangle, circle, triangle, heart shape)
A small mirror
Rulers and pencils
Scissors
Table of dimensions
Formula charts
Textbooks
Mathematical set

Rationale for the Lesson

Understanding plane shapes and symmetry helps pupils to recognise patterns and structures in their environment. This knowledge is important for developing spatial reasoning and forms a foundation for more advanced geometry concepts in higher classes.

Prerequisite/Previous Knowledge

Pupils can identify basic two-dimensional (2D) shapes such as squares, rectangles, circles, and triangles.

Lesson Content/Board Summary

PLANE SHAPES AND SYMMETRY

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 line of symmetry, both halves will match perfectly.

Shapes can be symmetrical or non-symmetrical.

Symmetrical shapes: Shapes that can be divided into two identical halves (e.g., square, rectangle, circle, heart).
Non-symmetrical shapes: Shapes that cannot be divided into two identical halves (e.g., some irregular polygons).

Line of Symmetry

A line of symmetry is an imaginary line that divides a shape into two identical halves. Each half is a mirror image of the other.

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

The number of lines of symmetry varies for different shapes:

Square: 4 lines of symmetry
Rectangle: 2 lines of symmetry
Circle: Infinite lines of symmetry
Equilateral triangle: 3 lines of symmetry
Isosceles triangle: 1 line of symmetry

Properties of Rectangles

The following are properties of rectangles:

It is a four-sided plane shape (quadrilateral).
Opposite sides are equal in length.
All four angles are right angles (90 degrees).
Opposite sides are parallel.
It has 2 lines of symmetry.

Properties of Squares

The following are properties of squares:

It is a four-sided plane shape (quadrilateral).
All four sides are equal in length.
All four angles are right angles (90 degrees).
Opposite sides are parallel.
It has 4 lines of symmetry.

Constructing Plane Shapes and Showing Symmetry Lines

Pupils can use rulers and pencils to draw shapes like squares and rectangles. They can then draw the lines of symmetry on these shapes using dashed lines to indicate them.

Quantitative Aptitude on Plane Shapes and Symmetry

This involves solving problems related to identifying symmetrical shapes, counting lines of symmetry, or applying properties of shapes like squares and rectangles to find missing lengths or angles.

Teaching Methods/Instructional Techniques

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

Instructional Procedures

Step 1: Introduction

Time: 5 minutes
Teaching Skill: Set Induction
Teacher’s Activity: The teacher greets the pupils and asks them to observe objects in the classroom, such as the chalkboard, windows, or the classroom door. The teacher asks, “What do you notice about these objects if you imagine folding them in half?”
Pupils’ Activity: Pupils respond, saying some objects look the same on both sides when folded.
Learning Point: Pupils recall basic observations about shapes and introduce the concept of matching halves.

Step 2: Explanation of Symmetry

Time: 10 minutes
Teaching Skill: Explanation/Demonstration
Teacher’s Activity: The teacher defines symmetry and line of symmetry using simple language. The teacher demonstrates with various cut-out paper shapes (e.g., a heart shape, an irregular shape) by folding them to show symmetrical and non-symmetrical examples. The teacher asks pupils to identify which shapes are symmetrical.
Pupils’ Activity: Pupils listen, observe the demonstrations, and identify symmetrical shapes.
Learning Point: Pupils understand the meaning of symmetry and can differentiate between symmetrical and non-symmetrical shapes.

Step 3: Identifying Lines of Symmetry

Time: 10 minutes
Teaching Skill: Practical Demonstration/Activity
Teacher’s Activity: The teacher distributes various cut-out paper shapes (square, rectangle, circle, triangle) to groups of pupils. The teacher guides them to fold each shape in different ways to find its line(s) of symmetry. The teacher demonstrates how to use a mirror to check for symmetry.
Pupils’ Activity: Pupils fold their paper shapes, identify the lines of symmetry, and draw them on the shapes. They count the lines of symmetry for each shape.
Learning Point: Pupils can locate and count the lines of symmetry for common plane shapes.

Step 4: Properties of Rectangles and Squares

Time: 7 minutes
Teaching Skill: Explanation/Questioning
Teacher’s Activity: The teacher draws a rectangle and a square on the board. The teacher asks pupils to state what they know about the sides and angles of these shapes. The teacher then formally states the properties of rectangles and squares, including their number of lines of symmetry.
Pupils’ Activity: Pupils respond to questions, listen attentively, and note down the properties.
Learning Point: Pupils can state the key properties of rectangles and squares.

Step 5: Constructing Shapes and Showing Symmetry

Time: 5 minutes
Teaching Skill: Guided Practice
Teacher’s Activity: The teacher demonstrates how to draw a square or rectangle accurately using a ruler and pencil. The teacher then shows how to draw the lines of symmetry on the drawn shape using dashed lines. The teacher asks pupils to try drawing a square and indicating its lines of symmetry.
Pupils’ Activity: Pupils draw a square or rectangle and indicate its lines of symmetry.
Learning Point: Pupils can construct basic plane shapes and show their lines of symmetry.

Step 6: Quantitative Aptitude on Plane Shapes and Symmetry

Time: 3 minutes
Teaching Skill: Problem-solving
Teacher’s Activity: The teacher presents a simple quantitative aptitude problem related to symmetry, e.g., “A square has how many lines of symmetry? If a rectangle has 2 lines of symmetry, what is the difference between the lines of symmetry of a square and a rectangle?” The teacher guides pupils to solve it.
Pupils’ Activity: Pupils attempt to solve the problem.
Learning Point: Pupils apply their understanding of symmetry to solve simple 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:

What is symmetry?
Mention two shapes that have lines of symmetry.
How many lines of symmetry does a square have?
State two properties of a rectangle.

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 main points of the lesson, emphasizing the importance of symmetry in identifying and understanding shapes. The teacher assigns homework: “Draw a rectangle and an equilateral triangle. Draw all their lines of symmetry.”
Pupils’ Activity: Pupils listen to the summary and copy the homework.
Learning Point: Pupils consolidate their learning and prepare for independent practice.

Home Task: Solve three new exercises on PLANE SHAPES. Show each step and check each answer.

Lesson Keywords

Symmetry – When a shape can be divided into two identical halves that mirror each other.
Line of Symmetry – An imaginary line that divides a shape into two identical parts.
Rectangle – A four-sided plane shape with opposite sides equal and all angles 90 degrees.
Square – A four-sided plane shape with all sides equal and all angles 90 degrees.
Plane shapes – Flat, two-dimensional shapes like squares, circles, and triangles.

Differentiation

For pupils who grasp the concept quickly, the teacher can challenge them to find shapes with more than four lines of symmetry or to identify objects in their environment that exhibit rotational symmetry. For pupils needing more support, the teacher can provide pre-drawn shapes for folding and cutting, or work with them in a small group to reinforce the basic definitions and demonstrations.

Note for teachers using this lesson plan

Ensure to have enough cut-out paper shapes for each pupil or group to engage in the practical folding activity. Emphasise the hands-on aspect of finding lines of symmetry. Encourage pupils to look for symmetry in everyday objects around them.