N2NumberFoundation

The Four Operations

Adding, subtracting, multiplying and dividing are the building blocks of all maths. This lesson covers written methods for big numbers and the order you must do operations in (BIDMAS).

30 min Video by Maths Genie AQA GCSE Maths

Multiplying Whole Numbers and DecimalsWatch the walkthrough, then read the notes below.

Open on YouTube

What you'll learn

Add and subtract using column methods
Multiply with long multiplication
Divide using short and long division
Use BIDMAS to do calculations in the right order

Written methods

For addition and subtraction, line the numbers up by place value and work from the right, carrying or borrowing as needed.

For multiplication, long multiplication multiplies by each digit in turn and adds the results. For division, short division (“bus stop”) works for dividing by a single digit.

Tip — Estimate the answer first (e.g. round to the nearest 10) so you can spot a silly mistake.

BIDMAS — the order of operations

When a calculation mixes operations, do them in this order: $B$ rackets, $I$ ndices, $D$ ivision and $M$ ultiplication, then $A$ ddition and $S$ ubtraction.

Brackets \to Indices \to \times \div \to + -

BIDMAS order of operations.

1Multiplication comes before addition.

4 \times 2 = 8

, then

3 + 8 = 11

Answer

11

Remember these

B I DM AS

Brackets, Indices, Divide/Multiply, Add/Subtract.

Watch out for these

Working left to right and getting

3 + 4 \times 2 = 14

Multiply first:

3 + 8 = 11

Forgetting to line digits up by place value in column methods.

Keep units under units, tens under tens, and the decimal points in line.

Key takeaways

Use neat column methods and estimate to check.
BIDMAS sets the order: Brackets, Indices, ×÷, +−.
Division and multiplication rank equally — work left to right between them.

Test yourself

Ready to practise The Four Operations? Pick a mode and earn XP & Dobloons.