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Maths

Order of operation

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BIDMAS

There is an agreed order of operations in Maths called BIDMAS.

BIDMAS stands for Brackets, Indices, Division and Multiplication, Addition and Subtraction

All of these terms are fairly obvious except for 'Indices', which are just powers (eg 23 or 42 etc.)

So the order you should do your calculations in is:

  • Brackets
  • Indices
  • Division and Multiplication. Start on the left and work them out in the order that you find them.
  • Addition and Subtraction. When only addition and subtraction are left in the sum work them out in the order you find them. starting from the left of the sum and working towards the right.

Example

What is 4 + 2 × 3?

If you calculate the '4 + 2' part first you get:
4 + 2 × 3 = 6 × 3 = 18

If you calculate the '2 × 3' part first you get:
4 + 2 × 3 = 4 + 6 = 10

These are two very different answers, but only one is correct.

In BIDMAS, multiplication comes before addition, so multiply 2 by 3 first.

4 + 2 × 3 = 4 + 6 = 10, so this is the right answer.

Example

What is 9 - 4 + 3?

This sum has only addition and subtraction. So work them out from left to right.

9 - 4 + 3 = 5 + 3 = 8

Notice that if you didn't go from left to right you would get a different answer:

9 - 4 + 3 = 9 - 7 = 2

But that would be the wrong answer. Always work them out from left to right.

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