Adding, Subtracting, Multiplying and Dividing are called **operator**s. Operators perform actions on numbers.

There are other operators, such as **indices** - these control operations such as squaring a number, or finding a square root.

**Brackets** **( )** are used to control the order in which calculations take place.

Each operation has a priority and control the sequence in which calculations are carried out:

• Brackets are always calculated first;

• Indices - such as 3^{2} - are calculated next;

• Divide - is next;

• Multipy (actually has the same priority as Division);

• Add - is then next;

• Subtract - (same priority as Addition).

This is known as **BIDMAS** (taking the first letter of each operation); sometimes it is also known as **BODMAS**.

When there is a mixture of operations in a calculation, the sequence of operations *must be carried out in BIDMAS order*.

Ellie has calculated 4 + 6 ÷ 2 = 5. Is she correct?

BIDMAS rules. The division has a higher priority than the addition and must be carried out first: 6 ÷ 2 = 3.

Then carry out the addition 4 + 3 = 7.

Answer: No

Put in brackets to make this calculation correct: 3 + 4^{2} = 49

Put brackets before the 3, and between the 4 and ^{2}.

The brackets make sure the addition is carried out first.

Answer: (3 + 4)^{2} = 49

See also Squares and Calculating with Indices

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