MYP · Mathematics MYP Year 3
Patterns, Sequences & Algebraic Thinking
22 min readStandardAssessed under MYP Mathematics Criterion B (Investigating Patterns) and Criterion C (Communicating) — a core strand in every Year 3 unit test and the eAssessment on-screen exam
Every question in this topic is really asking one thing: is the gap between terms constant (arithmetic), the ratio constant (geometric), or is it something else entirely? Get that classification right first and the formula, the graph, and the real-world story all fall into place. Get it wrong and every later mark bleeds away — so this is where you slow down, not speed up.
Overview: How This Topic Fits Together
A pattern is just a rule you can predict. In MYP Year 3 you meet that rule in three disguises: as a list of numbers (a sequence), as a picture (dots, tiles, matchsticks), and as a real situation (savings, seating, growth). The algebra — an nth-term rule — is the tool that lets you jump from 'term 20' to an answer without writing out 20 terms by hand.
- Arithmetic sequences grow by addition — same amount every step.
- Geometric sequences grow by multiplication — same factor every step.
- Some patterns (squares, triangular numbers) aren't linear at all — they need a second look at the differences of the differences.
- Every spatial or real-life pattern eventually reduces to one of these number behaviours — your job is to spot which one.
The shape of the chapter
Command terms you'll actually meet in this topic
| Command term | What it demands | AO | Mark-earning move |
|---|---|---|---|
| Calculate | Obtain a numerical answer, showing the relevant working stages. | Applying | A bare correct number with no visible subtraction/substitution step can still lose the process mark — always show the line of working. |
| Describe | Give a detailed, worded account of a rule or feature of the pattern. | Communicating | 'Add 3' alone is incomplete — say what is increasing and by how much, in a full sentence. |
| Explain | Give a reason, backed by evidence from the actual numbers or diagram given. | Communicating/Applying | Restating the claim ('it's arithmetic because it has a common difference') without pointing at the real values scores 0. |
| Justify | Give reasoning that proves a conclusion, usually via a check calculation. | Reasoning | You must compute and compare, not just assert — 'no, it's wrong' with nothing written down earns nothing. |
| Compare | State similarities AND differences between two or more items. | Reasoning | Giving only similarities (or only differences) caps the mark at roughly half. |
| State | Give a specific answer or formula with no explanation required. | Knowing | Some 'state' items are worth their own mark for writing the formula symbolically before you substitute anything. |
Key point
A sequence is arithmetic ⇔ constant difference between consecutive terms; geometric ⇔ constant ratio. Decide which one you're dealing with before reaching for a formula — mis-classifying the sequence is the single biggest cause of lost marks in this whole topic.
Overview