Class: Junior Secondary School 1 (JSS 1 / JS1)
Term: 3rd Term
Week: 2
Age: 12 years
Duration: 45 minutes
Subject: Mathematics
Curriculum Theme: Measurement and Geometry
Previous Lesson: Definition of Perimeter in Perimeter of Irregular and Regular Shapes.
Topic: Area of Irregular and Regular Shapes
Subject Matter: How to determine the area of a given plane shape; Derive the formula of regular shapes.

Specific Objectives

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

Cognitive Domain:

Define area.
Identify regular and irregular plane shapes.
State the formulas for calculating the area of squares, rectangles, and triangles.

Affective Domain:

Appreciate the importance of calculating area in real-life situations.
Show interest in solving problems related to area.

Psychomotor Domain:

Measure the dimensions of given regular shapes accurately.
Calculate the area of squares, rectangles, and triangles using appropriate formulas.
Estimate the area of irregular shapes by counting squares on a grid.

Work cooperatively in groups to solve area problems.

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 Junior Secondary Schools 1

Instructional Materials

The teacher will teach this lesson with the aid of:

Squared paper (graph paper)
Rulers and pencils
Cut-outs of various regular shapes (e.g., square, rectangle, triangle)
Cut-outs of irregular shapes (e.g., leaf, puddle shape)
Worksheets containing area problems.

Rationale for the Lesson

This lesson helps pupils understand how to measure the surface covered by different shapes. This knowledge is important for everyday tasks such as measuring land, painting a wall, or tiling a floor, providing a practical application of mathematics.

Prerequisite/Previous Knowledge

Pupils should have prior knowledge of basic plane shapes (squares, rectangles, triangles) and how to measure length and width.

Lesson Content/Board Summary

Area of Irregular and Regular Shapes

What is Area?

Area is the amount of surface covered by a two-dimensional shape. It is measured in square units (e.g., square centimeters (cm²) or square meters (m²)).

Area of Regular Shapes

Regular shapes are shapes with defined geometric properties, allowing their area to be calculated using specific formulas.

Area of a Square:
A square has four equal sides. Its area is calculated by multiplying the length of one side by itself.

Formula: Area = side × side = s²

Example 1: Calculate the area of a square with a side length of 5 cm.

Step 1: Write down the formula: Area = s²

Step 2: Substitute the side length: Area = 5 cm × 5 cm

Step 3: Calculate the area: Area = 25 cm²
Area of a Rectangle:
A rectangle has two pairs of equal sides (length and width). Its area is calculated by multiplying its length by its width.

Formula: Area = length × width = L × W

Example 2: Find the area of a rectangle with a length of 8 m and a width of 3 m.

Step 1: Write down the formula: Area = L × W

Step 2: Substitute the values: Area = 8 m × 3 m

Step 3: Calculate the area: Area = 24 m²
Area of a Triangle:
A triangle has three sides. Its area is calculated as half of the product of its base and its perpendicular height.

Formula: Area = ½ × base × height = ½bh

Example 3: A triangle has a base of 10 cm and a height of 6 cm. Calculate its area.

Step 1: Write down the formula: Area = ½bh

Step 2: Substitute the values: Area = ½ × 10 cm × 6 cm

Step 3: Calculate the area: Area = 30 cm²

Area of Irregular Shapes

Irregular shapes do not have standard geometric properties, so their area cannot be found using simple formulas. Their area can be estimated by placing them on a grid (squared paper) and counting the squares they cover.

Method for estimating area of irregular shapes:

Place the irregular shape on squared paper.
Count all the full squares completely inside the shape.
Count all the squares that are half or more covered by the shape (treat these as full squares).
Ignore squares that are less than half covered by the shape.
Add up the total number of full and more-than-half squares to get an approximate area.

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 briefly reviews the concept of perimeter. The teacher then introduces the topic of “Area of Irregular and Regular Shapes” by asking pupils to imagine painting a wall or tiling a floor and what they would need to know to buy enough paint or tiles.
Pupils’ Activity: Pupils respond to questions about perimeter and listen attentively to the introduction of the new topic.
Learning Point: Pupils recall previous knowledge and are introduced to the concept of area.

Step 2: Understanding Area

Time: 5 minutes
Teaching Skill: Explanation/Demonstration
Teacher’s Activity: The teacher defines area as the amount of surface covered by a shape and explains that it is measured in square units. The teacher uses a flat object like a book or a desk to demonstrate the surface.
Pupils’ Activity: Pupils listen to the definition and observe the teacher’s demonstration, asking questions for clarification.
Learning Point: Pupils understand the definition of area and its units.

Step 3: Area of Regular Shapes and Formulas

Time: 10 minutes
Teaching Skill: Lecture/Derivation
Teacher’s Activity: The teacher introduces regular shapes (square, rectangle, triangle) and explains that their areas can be found using formulas. The teacher guides pupils to recall the properties of these shapes and presents their respective area formulas on the board.
Pupils’ Activity: Pupils identify regular shapes and copy the formulas for the area of squares, rectangles, and triangles into their notebooks.
Learning Point: Pupils learn the formulas for calculating the area of common regular shapes.

Step 4: Worked Examples for Regular Shapes

Time: 10 minutes
Teaching Skill: Demonstration/Problem Solving
Teacher’s Activity: The teacher works through the examples for the area of a square, a rectangle, and a triangle as presented in the board summary, explaining each step clearly. The teacher emphasizes the importance of including units in the final answer.
Pupils’ Activity: Pupils follow the teacher’s steps, copy the examples, and ask questions about the calculation process.
Learning Point: Pupils learn how to apply the area formulas to solve problems involving regular shapes.

Step 5: Area of Irregular Shapes

Time: 5 minutes
Teaching Skill: Explanation/Visual Aid
Teacher’s Activity: The teacher explains that irregular shapes do not have simple formulas. The teacher demonstrates how to estimate the area of an irregular shape using squared paper by counting full and half-covered squares.
Pupils’ Activity: Pupils observe the demonstration and understand the method of estimating the area of irregular shapes.
Learning Point: Pupils learn a practical method for estimating the area of irregular shapes.

Step 6: Practical Activity

Time: 5 minutes
Teaching Skill: Group Work/Practical Application
Teacher’s Activity: The teacher distributes worksheets with various regular and irregular shapes. Pupils are asked to measure and calculate the area of regular shapes and estimate the area of irregular shapes using graph paper.
Pupils’ Activity: Pupils work individually or in small groups to complete the assigned tasks, applying the learned methods.
Learning Point: Pupils practice calculating and estimating areas, reinforcing their understanding.

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 area?
State the formula for the area of a rectangle.
Calculate the area of a square whose side is 7 cm.
How can you find the area of an irregular shape?

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 5 minutes
Teaching Skill: Summarization/Assignment
Teacher’s Activity: The teacher summarizes the key points of the lesson, reiterating the definitions of area, the formulas for regular shapes, and the method for irregular shapes. The teacher assigns homework from the textbook.
Pupils’ Activity: Pupils listen to the summary and copy the homework assignment.
Learning Point: Pupils consolidate their learning and are given tasks for further practice.

Home Task: Solve three new exercises on Area of Irregular and Regular Shapes. Show each step and check each answer.

Lesson Keywords

Area – The amount of surface covered by a shape.
Regular shapes – Shapes with defined geometric properties (e.g., square, rectangle, triangle).
Irregular shapes – Shapes without defined geometric properties.
Square – A four-sided regular shape with all sides equal.
Rectangle – A four-sided regular shape with opposite sides equal.
Triangle – A three-sided shape.
Formula – A mathematical rule expressed in symbols.
Grid – A pattern of horizontal and vertical lines, used for counting squares.

Differentiation

For pupils who grasp concepts quickly, provide more complex problems involving composite shapes made of regular figures. For pupils needing more support, offer additional guided practice with simpler shapes and provide pre-drawn grids for irregular shapes.

Note for teachers using this lesson plan

Emphasize the practical applications of area calculation to make the lesson more engaging. Ensure pupils understand the concept of square units and why they are used. Encourage precise measurement when pupils are working with cut-out shapes.