Change of Subject of Formulae

Grade 9 · Mathematics

Semester 1 | Period 3 | Week 13

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Subject: Mathematics

Semester: 1

Period: 3

Week: 13

WEEK 13
Class: Grade 9
Age: 14 years
Duration: 40 minutes of 5 periods
Subject: Mathematics
Topic: Change of Subject of Formulae
Focus: Addition, Multiplication, and Roots

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

  1. Rearrange formulae involving addition to make a given subject the subject of the formula.
  2. Rearrange formulae involving multiplication to make a given subject the subject of the formula.
  3. Rearrange formulae involving square roots to make a given subject the subject of the formula.
  4. Solve problems that require changing the subject of a formula.
  5. Apply the concept of change of subject to solve real-life mathematical problems.

INSTRUCTIONAL TECHNIQUES:
• Question and answer
• Guided demonstration
• Discussion
• Drills and exercises
• Real-life application

INSTRUCTIONAL MATERIALS:
• Whiteboard and marker
• Worksheets with formulae
• Formula cards
• Calculator (optional)
• Real-life problem scenarios

PERIOD 1 & 2: Change of Subject Involving Addition

PRESENTATION:

Step

Teacher’s Activity

Pupil’s Activity

Step 1 - Introduction

Introduces the concept of formulae and how to change the subject when dealing with addition.

Pupils listen and ask questions.

Step 2 - Explanation

Explains and demonstrates how to change the subject in simple addition formulae, e.g., A+B=C, make A the subject.

Pupils observe and ask questions.

Step 3 - Demonstration

Demonstrates with more complex examples, such as 2x+5=y solve for x.

Pupils take notes and work along with the teacher.

Step 4 - Note Taking

Teacher writes examples and explanations on the board.

Pupils copy the examples and take notes.

NOTE ON BOARD:

  1. A+B=C → A=C−B
  2. 2x+5=y → x=y−5

                                  2

EVALUATION (5 exercises):

  1. Rearrange the formula: x + 3 = 8
  2. Rearrange the formula: 3x + 4 = 10
  3. Make z the subject: 6z + 12 = 24
  4. Solve for y: 5 + y = 12
  5. Solve for a: a + 9 = 15

CLASSWORK (5 questions):

  1. Rearrange: A + 5 = B
  2. Rearrange: 10x + 2 = 50
  3. Make y the subject: 2y + 3 = 7
  4. Solve for z: 7 + z = 15
  5. Make b the subject: 5b + 3 = 8

ASSIGNMENT (5 tasks):

  1. Rearrange the formula: x + 4 = 12
  2. Rearrange the formula: 3x + 2 = 8
  3. Solve for p: 6p + 10 = 30
  4. Make y the subject: 8y + 9 = 18
  5. Rearrange: x + 7 = 15

 

PERIOD 3 & 4: Change of Subject Involving Multiplication

PRESENTATION:

Step

Teacher’s Activity

Pupil’s Activity

Step 1 - Introduction

Introduces changing the subject of formulae involving multiplication.

Pupils listen and ask questions.

Step 2 - Explanation

Explains the process of isolating the subject when formulae involve multiplication, e.g., ab=c , make a the subject.

Pupils observe and ask questions.

Step 3 - Demonstration

Solves more complex problems involving multiplication, such as 3x=y , make x the subject.

Pupils take notes and solve similar problems.

Step 4 - Note Taking

Teacher writes examples on the board for pupils to copy.

Pupils copy and practice.

NOTE ON BOARD:

  1. ab=c b = c/a
  2. 5x=20

5x = 20 → x=20/5=4

EVALUATION (5 exercises):

  1. Solve for x: 2x=10
  2. Solve for y: 4y=16
  3. Rearrange the formula: 7x=35
  4. Solve for bb: 3b=12
  5. Rearrange the formula: 6a=18

CLASSWORK (5 questions):

  1. Solve for m: 2m=8
  2. Rearrange: 4x=20
  3. Make y the subject: 5y=25
  4. Solve for x: 3x=21
  5. Rearrange: 10x=50

ASSIGNMENT (5 tasks):

  1. Solve for p: 5p=255p = 25
  2. Solve for n: 6n=366n = 36
  3. Rearrange the formula: 2x=14
  4. Solve for x: 3x=9
  5. Rearrange the formula: 7y=35

 

PERIOD 5: Change of Subject Involving Roots

PRESENTATION:

Step

Teacher’s Activity

Pupil’s Activity

Step 1 - Introduction

Introduces how to change the subject of formulae involving square roots.

Pupils listen and ask questions.

Step 2 - Explanation

Explains how to solve formulae that involve square roots, e.g., √a= b, make b the subject.

Pupils observe and ask questions.

Step 3 - Demonstration

Solves more complex problems, such as √x=y, solve for y

Pupils take notes and practice solving.

Step 4 - Note Taking

Teacher writes examples for pupils to copy.

Pupils copy and practice.

NOTE ON BOARD:

  1. √a=b → a=b² a =b²
  2. √x=y → x=y²  x = y²

EVALUATION (5 exercises):

  1. Solve for a: √a=5
  2. Rearrange the formula: √x=4
  3. Solve for z: √z=6
  4. Rearrange the formula: √b=3
  5. Solve for y: √y=7

CLASSWORK (5 questions):

  1. Solve for x: √x=10
  2. Rearrange: √y=8
  3. Solve for a: √a=12
  4. Rearrange: √n=5
  5. Solve for b: √b=9

ASSIGNMENT (5 tasks):

  1. Solve for c: √c=15
  2. Rearrange the formula: √m=7
  3. Solve for y: √y=2
  4. Rearrange the formula: √t=6
  5. Solve for p: √p=11