Order of operations and brackets · Usually met around P3
Brackets
Work out the brackets first.
How to do it
Method
Work out the brackets first
50 − (12 + 18) = 50 − 30 = 20
Another way
Take each away
50 − 12 − 18 = 38 − 18 = 20
In full
When there are brackets, work out what's inside them first: 50 − (12 + 18) → 12 + 18 = 30, then 50 − 30 = 20. Without brackets, 50 − 12 + 18 goes left to right and gives 56 — a different answer, so brackets change the order. (6 + 4) × 3 also starts inside: 6 + 4 = 10, then 10 × 3 = 30. Another way: taking away a sum is taking away each number in turn: 50 − (12 + 18) = 50 − 12 − 18 = 20, the same answer.
Worked examples
Have a go first, then open each one for the answer and the working.
Example 1
(19 + 2) × 3 = □
Show the answer and working
Answer: 63
Brackets first: 19 + 2 = 21, then 21 × 3 = 63.
Example 2
109 − (12 + 40) = 137
True or false?
Show the answer and working
Answer: False
Brackets first, 12 + 40, then take that from 109: 57.
Example 3
1398 − (409 + 164) = 1398 − □ = □
Fill in each box
Show the answer and working
Answer: 573，825
In the brackets 409 + 164 = 573; 1398 − 573 = 825.
Practise it in the game →Order of operations and brackets · Free to start, unlimited questions, no download