Describe & continue number patterns
Theory
A number pattern follows a rule, such as "add \(6\) each time" or "double each time". This Year 5 maths page shows how to find the rule by looking at the change from term to term, how to continue a pattern and fill gaps, and how to use patterns to solve problems.
Each number in a pattern is a term. The rule tells you how to get from one term to the next.
If the gap between terms is always the same, the rule is add (pattern goes up) or subtract (pattern goes down) that amount.
If the gaps keep growing (or shrinking), try multiply or divide: check whether each term is the one before times \(2\), times \(3\), or halved.
A pattern that adds an even number keeps every term odd or every term even, so you can tell whether a number will ever appear.
Kinds of rules:
| Pattern | What you see | Rule |
|---|---|---|
| \(7, 13, 19, 25\) | same gap, going up | add \(6\) |
| \(95, 87, 79, 71\) | same gap, going down | subtract \(8\) |
| \(7, 14, 28, 56\) | gaps growing | multiply by \(2\) |
| \(240, 120, 60, 30\) | gaps shrinking | divide by \(2\) |
Finding and using the rule
- Find the change from each term to the next.
- Same change: the rule is add or subtract it.
- Changing gaps: test multiply or divide by the same number.
- Check the rule on every term, then use it to continue the pattern.
Missing terms
- Find the rule from the terms you know.
- Apply it forwards into the gap, then check the next term still works.
| \(25 + 6\) | \(=\) | \(31\) |
| \(31 + 6\) | \(=\) | \(37\) |
Rule: add \(6\). Next terms \(31\) and \(37\).
| \(71 - 8\) | \(=\) | \(63\) |
| \(63 - 8\) | \(=\) | \(55\) |
Rule: subtract \(8\). Next terms \(63\) and \(55\).
| \(36 \times 3\) | \(=\) | \(108\) |
Rule: multiply by \(3\). Next term \(108\).
| \(30 \div 2\) | \(=\) | \(15\) |
Rule: halve (divide by \(2\)). Next term \(15\).
| \(16 - 9\) | \(=\) | \(7\) |
| \(16 + 7\) | \(=\) | \(23\) |
\(23\). Check: \(23 + 7 = 30\).
No. The pattern starts odd and adds \(4\) (even), so every term is odd, and \(50\) is even.
| \(15 + 3 \times 8\) | \(=\) | \(39\) |
\(\$39\) (week 2: \(\$23\), week 3: \(\$31\), week 4: \(\$39\)).
| \(200 - 4 \times 12\) | \(=\) | \(152\text{ L}\) |
\(152\) L.
Common pitfalls
Frequently asked questions
What is the rule of a pattern?
The instruction that gets you from one term to the next, like "add 6" or "double".
How do I find the rule?
Look at the change between terms. Same change: add or subtract. Growing changes: try multiplying.
How do I find a missing term?
Find the rule from the other terms and apply it: \(16 + 7 = 23\).
How can I tell if a number is in a pattern?
Continue the pattern past the number, or look for a property such as every term being odd.
What is a doubling pattern?
Each term is two times the one before: \(7, 14, 28, 56\).