MYP · Mathematics MYP Year 2
Ratio, Proportion & Percentages
22 min readStandardCore Number & Algebra strand — assessed mainly under MYP Criterion A (Knowing & Understanding) and Criterion C (Communicating); real-life context questions (money, graphs, tables) appear almost every unit test and the eAssessment.
Ratio, proportion and percentage are three faces of the same idea — comparing quantities multiplicatively rather than by subtraction. Once you see , and 'x%' as the same relationship written three different ways, half of this chapter's exam questions become recognition, not calculation.
Overview — The Shape of the Chapter
Every question in this topic asks the same underlying question: does one quantity change in a fixed, predictable multiple of the other? If yes, you've got proportion or percentage. If a flat fee, starting amount or fixed charge gets added on top, that clean relationship breaks — and spotting exactly when it breaks is what separates full marks from partial marks on 'Explain' questions.
The shape of the chapter
Command term guidance
| Command term | What it demands | AO | Mark-earning move |
|---|---|---|---|
| State | Give a short answer with no working required | AO1 | 1 mark for the correct value alone — no justification needed, but an unsupported wrong guess scores nothing |
| Identify | Pick out a specific feature (value, pattern, piece of evidence) from data given | AO1 | 1 mark for naming the exact feature — e.g. 'C ÷ n = 3 for every row' scores; 'the numbers go up evenly' does not |
| Calculate | Produce a numerical answer with clear working | AO2 | Method mark for correct setup even with an arithmetic slip; final mark needs correct units and sensible rounding |
| Describe | Give a detailed account of a pattern or feature in words | AO1/AO2 | Needs more than one fact — a single-fact answer caps the mark |
| Explain | Give the reason WHY, not just what happened | AO2/AO3 | Marks reward the causal link, not a restatement of the situation |
| Compare | State a similarity AND a difference between two models/values | AO3 | Both must be explicit — one alone caps the mark below full credit |
Key point
Ratio, direct proportion and percentage all describe the SAME multiplicative relationship — the moment a fixed amount is added or subtracted (a fee, a flat charge, a starting value), the relationship stops being a 'clean' proportion, even if both quantities still increase together.
Overview