BIDMAS explained.

1. What’s Going
Wrong?

2. Find a solution to these questions without using a
calculator.
a 8 + 16 ÷ 4 =
Did you get 6 or 12?
b 8 + 4 × 6 =
Did you get 32 or 72?
c 2 × 6 + 4 ÷ 2 =
Did you get 6, 8 or 12?
d 7 – 4 ÷ 2 + 3 =
Did you get 0.6, 2, 4.5, 6.2 or 8?
There is more
than one
solution.

3. How can we get so many different answers?
Aren’t we all supposed to get the same answer if
we do the same calculation?
If you have a scientific calculator it will be
programmed to tell you the ‘correct’ answer, but if
you don’t, then you need to be able to follow some
rules that make sure we all get the same answer.

4. B
I
D
M
A
S
RACKETS
NDICES
IVISION
ULTIPLICATION
DDITION
UBTRACTION
This is the order we have
to do calculations in.
The rule is called BIDMAS or you may know it as
BODMAS.
Each of the letters stands for something different.

5. 8 × 2 = 16
Now let’s try using BIDMAS to solve some problems.
The first thing we need to do is work out the Brackets.
Solve (3 + 5) × 2 =
Put the 8 in place of the brackets and do the Multiplication.
(3 + 5) × 2 =
So, 3 + 5 is 8
Example 1

6. Solve 36 – 32 =
So, 32 is 9
36 – 9 = 27
Now try this one before looking at the solution.
This time we need to do the Indices first.
Put the 9 in place of the 32 and do the Subtraction.
Example 2
36 – 32 =

7. Now try these without a calculator. Worked solutions
are on the following slides.
a 14 + 30 ÷ 5 =
b 10 – 23 =
c 6 + 4 ÷ 2 + 32 =
d 2 + (4 + 3)2 =
e (7 + 1)2 + (10 – 6)2 =

8. Solution A
14 + 30 ÷ 5 =
The first thing we need to do is work out the Division
So, 30 ÷ 5 = 6
Then we do the Addition
14 + 6 = 20

9. Solution B
10 – 23 =
We work out the Indices first
So, 23 = 8
Then we do the Subtraction
10 – 8 = 2

10. Solution C
6 + 4 ÷ 2 + 32 =
The first thing to do is work out the Indices
So, 32 = 9
Next, we work out the Division
4 ÷ 2 = 2
Then we do the Addition
6 + 2 + 9 = 17

11. Solution D
2 + (4 + 3)2 =
First we work out the Brackets
4 + 3 = 7
Next we work out the Indices
(4 + 3)2
72 = 49
Then we do the Addition
2 + 49 = 51

12. Solution E
(7 + 1)2 + (10 – 6)2 =
First we work out the Brackets (this time there are two
brackets)
7 + 1 = 8
10 – 6 = 4
Next we work out the Indices
82 = 64
42 = 16
Then we work out the Addition
64 + 16 = 80