Form 1 Unit 1: Lesson 4 – Order Of Operations

Objective:

At the end of the lesson, students should know the correct order to carry out mathematical calculations.

When we say operation, we mean using the symbols of addition, subtraction, multiplication or division to carry out calculations. In using these symbols in a mathematical sentence, we need to know the order in which they operate else we will end up getting different results. Every mathematical sentence in a bracket should be done before any other operation outside the bracket.

 

Example 1

Work out the value of 6 + 4 – (3 x 9)

Solution

6 + 4 – (3 x 9)

6 + 4 – (27)

10 27 = – 17

 

Example 2

Work out the value of 4 + 8 × 7.

Solution

4 + 8 × 7

= 4 + 56      ( 8 × 7 is 56),

= 60.

 

NOTE

If you work out 4 + 8 then multiply by 7, you will get 84 which is wrong.

MATHEMATICIANS HAVE AGREED TO FOLLOW A PARTICULAR ORDER WHEN CALCULATIONS INVOLVE SEVERAL OPERATIONS;

BODMAS

 Brackets

Order/ Divide /Multiply

Add/Subtract.

Work out sums in the brackets first, and then multiplication and division are done next with equal priority. Addition and subtraction are done last with equal priority.

Example 3

6 + –7 + 10 ÷ 2

Solution

6 + – 7 + 10 ÷ 2

6 7 + 5

= – 1 + 5

= + 4

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