Form 1 Unit 1: Lesson 2 – The 4 Operations & Whole Numbers

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