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YOU ARE LEARNING:

BIDMAS

BIDMAS

lesson introduction

BIDMAS

When a calculation involves multiple operations, we must decide which order to perform our operations

The order we carry out calculations like $+$ , $-$ , $\times$ or $\div$ affects the final answer. What is the correct order to carry them out?

1

BIDMAS tells us the order of operations

Brackets come first, while addition and subtraction come last.

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2

Always follow this order when answering a question

This is true of all calculations.

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3

Would you do multiplication before or after addition?

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Let's try this example together: $6 + 5 \times 3$

1

We will walk through this step by step

Don't forget that BIDMAS gives us the order of operations

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2

We have two operations here: addition $+$ and multiplication $\times$ Using BIDMAS, which one do we calculate first?

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3

What is $5 \times 3$ ?

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4

Now we use the value we've just found

The calculation is now $6 + 15$

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5

What is $6 + 15$ ?

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6

Good work!

The final answer is $21$

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1

Division and Multiplication are equal (as they are opposite operations). If they appear in the same question, go from left to right.

This also applies to Addition and Subtraction.

2

There is one tricky thing about BIDMAS when it comes to addition and subtraction.

When it is just addition and subtraction, we must work from left to right.

3

The correct answer is found by working from left to right. What is $24-10+4$ ?

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4

But what happens if we do the addition first?

We know that $10+4=14$ .

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5

What is the final answer now?

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6

It's not possible for both of these answers to be correct!

Remember when it is just addition and subtraction, work from left to right.

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Now let's try working out this one: $7^2 - 3 \times 8 + 2$

1

This one has a few more operations

And we will walk through it step by step

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2

We have four operations here

Indices $7^2$ subtraction $7^2-3$ , multiplication $3 \times 8$ ,
addition $8+2$

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3

Which operation do we do first?

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4

So what is $7^2$ ?

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5

Multiplication is the next step. What is $3\times8$ ?

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6

Let's put these into our calculation

It now looks like $49-24+2$

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7

What happens next?

Addition and subtraction are equal in order, so we perform from left to right.

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8

What is $49-24+2$ ?

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9

Nice! 👍

The final answer is $27$

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Here is a quick test before we move on.

What is $2 + 3 \times 4$ ?

And how about $5 \times 3^2$ ?

This is a slightly harder one!

1

This exercise will use all of the operations

Let's walk through it step by step....

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2

Tackle the brackets in the numerator first

B is the first letter in BIDMAS

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3

Which operation do we do first?

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4

What is $8 \times 2$ ?

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5

Subtract $4$ from $16$

$16-4=12$

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6

Now we can tackle the set of brackets in the denominator. Do the indices first

$1^2=1$

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7

Finish the calculation in the bracket by adding the numbers together

$1+3=4$

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8

Divide the numerator by the denominator

$\dfrac{12}{4}=3$

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9

Nice!

The final answer is $3$

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Find $\dfrac{(7-2^2)}{(4^2-15)}$ .

Feel free to take your time working this one out. You may need to write your workings down.

1

Summary! BIDMAS tells us the order of operations

Brackets come first, while addition and subtraction come last.

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2

If we only have addition and subtraction we must work from left to right.

Do the calculation as if you were reading it

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