Order of operations & grouping symbols - With brackets
Theory
Brackets ( ) are grouping symbols. They say "work this part out first". \(9 + 6 \times 3 = 27\), but \((9 + 6) \times 3 = 45\). This Year 6 maths page shows how to work out number sentences with brackets, including brackets inside brackets, and how to place brackets to make a number sentence true.
Brackets group part of a number sentence. The part inside the brackets is worked out first, before any other operation.
After the brackets, use the usual order: \(\times\) and \(\div\) before \(+\) and \(-\); equal rank from left to right.
With brackets inside brackets, start with the innermost pair and work outwards.
Brackets can also just make the order clear: \(5 + (3 \times 6)\) has the same value as \(5 + 3 \times 6\), because the multiplication would be done first anyway.
Brackets come first:
Working out a number sentence with brackets
- Work out the inside of each pair of brackets (innermost first).
- Rewrite the line with that answer in place of the brackets.
- Finish with \(\times\) and \(\div\), then \(+\) and \(-\).
Placing brackets to make a sentence true
- Try brackets around different pairs of numbers.
- Work out each try until one gives the target.
(i) \((9 + 6) \times 3\)
(ii) \(9 + 6 \times 3\)
| \(15 \times 3\) | \(=\) | \(45\) |
| \(9 + 18\) | \(=\) | \(27\) |
(i) \(45\)
(ii) \(27\)
| \(6 \times (11 - 4)\) | \(=\) | \(6 \times 7\) |
| \(6 \times 7\) | \(=\) | \(42\) |
\(42\).
| \(72 \div (3 + 5)\) | \(=\) | \(72 \div 8\) |
| \(72 \div 8\) | \(=\) | \(9\) |
\(9\).
| \(60 - (14 + 9)\) | \(=\) | \(60 - 23\) |
| \(60 - 23\) | \(=\) | \(37\) |
\(37\).
| \(4 \times (15 - 8)\) | \(=\) | \(4 \times 7\) |
| \(4 \times 7\) | \(=\) | \(28\) |
\(28\), as in the second diagram.
| \((30 + 6) \div (7 - 3)\) | \(=\) | \(36 \div 4\) |
| \(36 \div 4\) | \(=\) | \(9\) |
\(9\).
| \((5 + 3) \times 6\) | \(=\) | \(48\) |
\((5 + 3) \times 6 = 48\). Without brackets the value is \(23\).
| \(9 \times (4 + 3)\) | \(=\) | \(9 \times 7\) |
| \(9 \times 7\) | \(=\) | \(63\) |
\(\$63\).
| \(4 \times (7 + 2)\) | \(=\) | \(4 \times 9\) |
| \(4 \times 9\) | \(=\) | \(36\) |
She ignored the brackets and did \(4 \times 7 + 2\). The brackets come first: the answer is \(36\).
Common pitfalls
Frequently asked questions
What do brackets mean in a number sentence?
Work out the part inside the brackets first.
What is (9 + 6) Γ 3?
\(15 \times 3 = 45\).
What if there are brackets inside brackets?
Work out the innermost brackets first, then work outwards.
Do brackets always change the answer?
No. They only change it if they change which operation is done first.
How do I place brackets to get a target?
Try grouping different pairs and work each one out until you hit the target.