__Objective__

At the end of the lesson the student should be able to:

- Add and subtract whole numbers.
- Multiple and divide whole numbers.
- Understand and apply the relationship between addition and multiplication.
- Understand and apply the relationship between subtraction and division.

__Addition and Subtraction__

To add and subtract effectively and easily, it is advisable to write the numbers under their place values.

**When adding and subtracting, remember that:**

- adding or subtracting
**zero**leaves any number unchanged e.g. 7+**0**=7, 8 –**0**=8 - Changing the
**order**does**not**change the result for addition e.g. 6 + 8=8 + 6=14 - However, when you change the order of a subtraction, the result changes 6 – 3 ≠ 3 – 6
- When adding more than two numbers we can group them in any order:

(2+3)+8= (2+8) +3= (3+8) +2, etc.

__Example 1__

Work out the value of a) 4 + 8 +7 b) 7963-498

__Solution__:

4+8+7 =19

Always arrange numbers in their place values before adding or subtracting.

__Multiplication of Whole Numbers__

Multiplication is the process of repeated addition.

6 + 6 +6 = 6 × 3 =18

The commutative law is true for all multiplication.

6 × 7=7 × 6

A × B=B × A

__Example __

Simplify 40 × 86

__Solution__

40 × 86 = 3440

__Dividing Whole Numbers.__

Division is the process of finding out how many times one number can be subtracted from another. It is the opposite of multiplication.

__Example 1__

How many 4’s are in 24?

__Solution __

4’s in 24 = 24-4-4-4-4-4-4 = 0

24 divided by 4 equals 6

24 ÷ 4=6

Note

a remainder occurs if the divisor is not a factor of the dividend.

The commutative law of does not hold true for division

4 ÷ 5≠5 ÷ 4

A ÷ B ≠B ÷ A

Division of any number by zero is not possible

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