📘 Lesson Note: Simple Equations
Subject: Mathematics
Class: Basic 4
Topic: Simple Equations
Duration: 40 minutes
Learning Objectives
At the end of the lesson, pupils should be able to:
- Explain what an equation is.
- Identify the unknown number in a simple equation.
- Solve simple addition equations.
- Solve simple subtraction equations.
- Solve simple multiplication and division equations.
- Check their answers.
1. Meaning of an Equation
An equation is a mathematical statement that shows that two quantities are equal.
The symbol = means “is equal to.”
For example:
5 + 3 = 8
Both sides have the same value, so it is an equation.
2. What is an Unknown Number?
Sometimes a number in an equation is missing. We can use a letter or a box to represent the missing number.
For example:
□ + 4 = 9
We ask: What number plus 4 gives 9?
The answer is 5.
Therefore:
□ + 4 = 9
5 + 4 = 9
So, □ = 5.
3. Solving Addition Equations
When the unknown number is being added to another number, we can use subtraction to find it.
Example 1
x + 6 = 14
To find x:
x = 14 − 6
x = 8
Therefore, x = 8.
Example 2
□ + 9 = 20
□ = 20 − 9
□ = 11
4. Solving Subtraction Equations
Example 1
x − 5 = 12
To find x, add 5 to 12:
x = 12 + 5
x = 17
Therefore, x = 17.
Example 2
□ − 8 = 10
□ = 10 + 8
□ = 18
5. Solving Multiplication Equations
When an unknown number is multiplied by another number, we can use division to find the unknown.
Example 1
x × 4 = 20
x = 20 ÷ 4
x = 5
Therefore, x = 5.
Example 2
□ × 6 = 30
□ = 30 ÷ 6
□ = 5
6. Solving Division Equations
Example 1
x ÷ 3 = 7
To find x, multiply 7 by 3:
x = 7 × 3
x = 21
Therefore, x = 21.
Example 2
□ ÷ 5 = 6
□ = 6 × 5
□ = 30
⭐ Easy Rules to Remember
| Equation | Operation to Find the Unknown |
|---|---|
| x + 5 = 12 | 12 − 5 |
| x − 5 = 12 | 12 + 5 |
| x × 5 = 20 | 20 ÷ 5 |
| x ÷ 5 = 4 | 4 × 5 |
Remember: We use the opposite operation to find the unknown number.
- Addition ↔ Subtraction
- Multiplication ↔ Division
7. Checking an Answer
After solving an equation, we should put our answer back into the original equation.
Example
x + 7 = 15
We find:
x = 15 − 7 = 8
Now check:
8 + 7 = 15 ✅
Therefore, our answer is correct.
📝 Class Activity
Solve these equations:
- x + 5 = 13
- x + 8 = 20
- x − 6 = 10
- x − 9 = 15
- x × 3 = 18
- x × 5 = 25
- x ÷ 4 = 6
- x ÷ 5 = 7
Answers
- x = 8
- x = 12
- x = 16
- x = 24
- x = 6
- x = 5
- x = 24
- x = 35
🎯 Evaluation Questions
- What is an equation?
- What does the symbol = mean?
- Find the missing number: x + 7 = 15
- Find x: x − 8 = 12
- Find x: x × 4 = 28
- Find x: x ÷ 5 = 6
- What operation can we use to solve x + 9 = 20?
- What operation can we use to solve x × 3 = 18?
Homework
Solve the following:
- x + 12 = 25
- x − 7 = 18
- x + 15 = 30
- x − 9 = 21
- x × 6 = 42
- x × 8 = 56
- x ÷ 4 = 9
- x ÷ 7 = 5