Simple Equation

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📘 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:

  1. Explain what an equation is.
  2. Identify the unknown number in a simple equation.
  3. Solve simple addition equations.
  4. Solve simple subtraction equations.
  5. Solve simple multiplication and division equations.
  6. 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:

  1. x + 5 = 13
  2. x + 8 = 20
  3. x − 6 = 10
  4. x − 9 = 15
  5. x × 3 = 18
  6. x × 5 = 25
  7. x ÷ 4 = 6
  8. x ÷ 5 = 7

Answers

  1. x = 8
  2. x = 12
  3. x = 16
  4. x = 24
  5. x = 6
  6. x = 5
  7. x = 24
  8. x = 35

🎯 Evaluation Questions

  1. What is an equation?
  2. What does the symbol = mean?
  3. Find the missing number: x + 7 = 15
  4. Find x: x − 8 = 12
  5. Find x: x × 4 = 28
  6. Find x: x ÷ 5 = 6
  7. What operation can we use to solve x + 9 = 20?
  8. What operation can we use to solve x × 3 = 18?

Homework

Solve the following:

  1. x + 12 = 25
  2. x − 7 = 18
  3. x + 15 = 30
  4. x − 9 = 21
  5. x × 6 = 42
  6. x × 8 = 56
  7. x ÷ 4 = 9
  8. x ÷ 7 = 5
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