Class 7 Maths- BODMAS Rule

BODMAS rule

"Operations" mean things like add, subtract, multiply, divide, squaring, etc. If it isn't a number it is probably an operation.

But, when you see something like...

8 + (6 × 4 + 3)

... what part should you calculate first? 

Start from the left and go to the right? 

Or go from right to left?

If we calculate them in the wrong order, we will get a wrong answer !

So, long ago people agreed to follow rules when doing calculations, and they are:

Order of Operations

Do things in Brackets First. Example:

		5 × (5 + 3)	=	5 × 8	=	40

Exponents (Powers, Roots) before Multiply, Divide, Add or Subtract. Example:

5 × 22

=

5 × 4

=

20

Multiply or Divide before you Add or Subtract. Example:

		2 + 2 × 3	=	2 + 6	=	8

Otherwise just go left to right. Example:

		30 ÷ 5 × 3	=	6 × 3	=	18

BODMAS: BODMAS is used for helping us remember the order for dealing with mathematical operators in a mathematic statement.

BODMAS rules: B–Brackets, O–Then order (powers), D–Division, M–Multiplication, A–Addition and S-Subtraction.

Divide and Multiply rank equally (and go left to right).

Add and Subtract rank equally (and go left to right)

Let us now go through a few examples which will help us to understand ‘BODMAS’ better.

(a) 25 - 48 ÷ 6 + 12 × 2

Solution:

25 - 48 ÷ 6 + 12 × 2

= 25 - 8 + 12 × 2, (Simplifying ‘division’ 48 ÷ 6 = 8)

= 25 - 8 + 24, (Simplifying ‘multiplication’ 12 × 2 = 24)

= 17 + 24, (Simplifying ‘subtraction’ 25 - 8 = 17)

= 41, (Simplifying ‘addition’ 17 + 24 = 41)

Answer: 41

(b) 78 - [5 + 3 of (25 - 2 × 10)]

Solution:

78 - [5 + 3 of (25 - 2 × 10)]

= 78 - [5 + 3 of (25 - 20)], (Simplifying ‘multiplication’ 2 × 10 = 20)

= 78 - [5 + 3 of 5], (Simplifying ‘subtraction’ 25 - 20 = 5)

= 78 - [5 + 3 × 5], (Simplifying ‘of’)

= 78 - [5 + 15], (Simplifying ‘multiplication’ 3 × 5 = 15)

= 78 - 20, (Simplifying ‘addition’ 5 + 15 = 20)

= 58, (Simplifying ‘subtraction’ 78 - 20 = 58)

Answer: 58