Order of operations & grouping symbols - Two operations
Theory
When a number sentence has more than one operation, everyone must do them in the same order to get the same answer. Multiply and divide before you add and subtract. When the operations are equal in rank (only \(+\) and \(-\), or only \(\times\) and \(\div\)), work from left to right. This Year 6 maths page shows how to use these rules with two operations and how to write number sentences for word problems.
An operation is \(+\), \(-\), \(\times\) or \(\div\). The order of operations is the agreed order for working them out.
Multiplication and division come before addition and subtraction, wherever they are in the line. In \(9 + 2 \times 7\), do \(2 \times 7\) first.
Multiplication and division have equal rank, and so do addition and subtraction. Operations of equal rank are worked from left to right: \(18 - 7 + 4 = 11 + 4 = 15\).
Brackets change the order: anything in brackets is worked out first. (Brackets are covered fully on the brackets page.)
The rules for two operations:
Working out a number sentence with two operations
- Look for \(\times\) or \(\div\). If there is one (and a \(+\) or \(-\)), do it first.
- If both operations are the same rank, work from left to right.
- Rewrite the line after each step so you can see what is left.
| \(9 + 2 \times 7\) | \(=\) | \(9 + 14\) |
| \(9 + 14\) | \(=\) | \(23\) |
\(23\).
| \(8 \times 6 - 10\) | \(=\) | \(48 - 10\) |
| \(48 - 10\) | \(=\) | \(38\) |
\(38\).
| \(35 - 21 \div 7\) | \(=\) | \(35 - 3\) |
| \(35 - 3\) | \(=\) | \(32\) |
\(32\), as in the second diagram.
| \(18 - 7 + 4\) | \(=\) | \(11 + 4\) |
| \(11 + 4\) | \(=\) | \(15\) |
\(15\). (Adding first would give \(7\), which is wrong.)
(i) \(11 + 4 \times 9\)
(ii) \(56 \div 8 + 3\)
(iii) \(90 - 5 \times 12\)
| \(11 + 36\) | \(=\) | \(47\) |
| \(7 + 3\) | \(=\) | \(10\) |
| \(90 - 60\) | \(=\) | \(30\) |
(i) \(47\)
(ii) \(10\)
(iii) \(30\)
| \(48 \div 4 \div 2\) | \(=\) | \(12 \div 2\) |
| \(12 \div 2\) | \(=\) | \(6\) |
\(6\).
| \(6 \times 8 + 5\) | \(=\) | \(48 + 5\) |
| \(48 + 5\) | \(=\) | \(53\) |
\(6 \times 8 + 5 = 53\) rolls. The order rules mean no brackets are needed.
| \(4 + 5 \times 6\) | \(=\) | \(4 + 30\) |
| \(4 + 30\) | \(=\) | \(34\) |
He added first. Multiplication comes first, so the answer is \(34\).
Common pitfalls
Frequently asked questions
What is the order of operations?
The agreed order: brackets first, then multiplication and division, then addition and subtraction.
Do you always work from left to right?
Only for operations of equal rank. Multiply and divide before you add and subtract.
What is 9 + 2 Γ 7?
\(9 + 14 = 23\).
Which comes first, addition or subtraction?
Neither: work them from left to right.
Why do we need these rules?
So that everyone gets the same answer from the same number sentence.