Class: Junior Secondary School 3 (JSS3, JSS 3)
Term: 2nd Term
Week: 6
Age: 14 years
Duration: 45 minutes
Subject: Mathematics
Curriculum Theme: Mathematics
Previous Lesson: Similar Shapes
Topic: Enlargement And Scale Factor
Subject Matter: Meaning of enlargement and scale factor, Enlargement shapes using scale factor, Calculating and comparing lengths, areas and volumes of similar figures

Specific Objectives

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

Cognitive Domain:
(a) Explain enlargement and scale factor.
(b) Calculate enlarged dimensions of shapes.
Affective Domain:
(a) Show interest in using scale drawings in real-life situations.
Psychomotor Domain:
(a) Construct enlarged figures using a given scale factor.
Social Domain:
(a) Collaborate effectively during group enlargement tasks.

Reference Materials

The following resources was used in planning this lesson:

9 Years Basic Education Curriculum
Lagos State Unified Scheme of Work for Junior Secondary Schools
Cuemath – Scale Factor – Formula, Meaning, Examples
Relevant Textbooks

Instructional Materials

The teacher will teach this lesson with the aid of:

Graph sheets
Rulers and pencils
Charts showing enlarged shapes
Projector or printed visual aids
Geometric models

Rationale for the Lesson

Understanding enlargement helps pupils interpret scale drawings, maps, models and apply proportional reasoning in real-life situations.

Prerequisite/Previous Knowledge

Pupils are familiar with basic shapes, similarity, ratio and simple proportional calculations from previous classes.

Lesson Content/Board Summary

Lesson Content

Enlargement and Scale Factor

Meaning of Enlargement

Enlargement is the process of increasing the size of a shape while keeping its proportions the same. All the sides of the enlarged shape are in the same ratio to the original.

The following are key points about enlargement:

Enlargement changes the size but keeps the shape proportional.
The position of the enlarged shape depends on the centre of enlargement.
Enlargement can increase or reduce a shape depending on the scale factor.

Meaning of Scale Factor

Scale factor is the number that shows how many times a shape is enlarged or reduced. It determines the ratio between the original shape and the enlarged one.

The following are facts about scale factor:

A scale factor greater than 1 produces an enlarged shape.
A scale factor between 0 and 1 produces a reduced shape.
The lengths, areas and volumes change proportionally to the scale factor.

Enlargement of Shapes Using Scale Factor

Enlargement involves multiplying every side of a shape by the scale factor to produce a new shape.

Examples include:

A triangle with sides 3 cm, 4 cm, 5 cm enlarged by scale factor 2 becomes 6 cm, 8 cm, 10 cm.
A rectangle 5 cm × 2 cm enlarged by scale factor 3 becomes 15 cm × 6 cm.
A square of side 4 cm reduced by scale factor ½ becomes side 2 cm.

Calculating and Comparing Lengths, Areas and Volumes of Similar Figures

When shapes are similar, their lengths, areas and volumes change according to the scale factor.

These include:

Lengths are multiplied by scale factor (k).
Areas are multiplied by scale factor squared (k²).
Volumes are multiplied by scale factor cubed (k³).

Teaching Methods/Instructional Techniques

Discussion, Lecture, Explanation, Demonstration, Group Work, Visual Aids

Instructional Procedures

To deliver this lesson, the teacher will adopt the following steps:

Step 1: Introduction (Set Induction)

Time: 5 minutes
Teaching Skill: Set Induction
Teacher’s Activity: The teacher shows two pictures, one small and one enlarged, and asks pupils to identify the difference.
Pupils’ Activity: Pupils observe and respond.
Learning Point: Pupils become aware of the concept of enlargement.

Step 2: Meaning of Enlargement

Time: 7 minutes
Teaching Skill: Explanation
Teacher’s Activity: The teacher explains enlargement and outlines key features.
Pupils’ Activity: Pupils listen and ask questions.
Learning Point: Pupils understand the meaning of enlargement.

Step 3: Meaning of Scale Factor

Time: 8 minutes
Teaching Skill: Discussion
Teacher’s Activity: The teacher defines scale factor and explains how it affects size changes.
Pupils’ Activity: Pupils participate in discussion.
Learning Point: Pupils understand scale factor and its use.

Step 4: Enlargement Using Scale Factor

Time: 10 minutes
Teaching Skill: Demonstration
Teacher’s Activity: The teacher demonstrates how to enlarge shapes using scale factor and solves examples.
Pupils’ Activity: Pupils construct enlarged shapes on graph sheets.
Learning Point: Pupils learn how to calculate enlarged dimensions.

Step 5: Calculating and Comparing Lengths, Areas and Volumes

Time: 7 minutes
Teaching Skill: Guided Practice
Teacher’s Activity: The teacher shows worked examples on scaling lengths, areas and volumes.
Pupils’ Activity: Pupils solve teacher-given exercises.
Learning Point: Pupils understand how scale factor affects different dimensions.

Step 6: Note-Taking

Time: 3 minutes
Teaching Skill: Reinforcement
Teacher’s Activity: The teacher instructs pupils to copy the board summary.
Pupils’ Activity: Pupils write notes.
Learning Point: Pupils retain key concepts.

Step 7: Evaluation/Review

Time: 4 minutes
Teaching Skill: Questioning
Teacher’s Activity:
The teacher evaluates the learning by asking the following questions:

What is enlargement?
What is scale factor?
What happens when the scale factor is greater than 1?
Enlarge a shape with side 3 cm by scale factor 3.
State how areas change when the scale factor is doubled.
Pupils’ Activity: Pupils answer questions.
Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 1 minute
Teaching Skill: Closure
Teacher’s Activity: The teacher summarises the lesson and connects it to real-life uses.
Pupils’ Activity: Pupils listen.
Learning Point: Pupils recall the main points learned.

Lesson Keywords

Enlargement – increasing the size of a shape
Scale Factor – the ratio used to enlarge or reduce a figure
Similarity – when two shapes have the same shape but different sizes
Proportion – comparison of sizes using ratios
Dimensions – measurements of length, area or volume

Differentiation

Provide simplified tasks for slow learners, while fast learners work on more complex enlargement problems. Use visual aids for learners needing more support.

Note for teachers using this lesson plan

Ensure pupils use accurate measurements during construction. Encourage group cooperation and monitor for errors in ratio application.