MYP Maths: Communicating Maths Clearly (Criterion C) Explained

Criterion C is marked out of 8 using four descriptor bands (1-2, 3-4, 5-6, 7-8), judging whether your working uses correct mathematical language, appropriate representations (tables, graphs, diagrams) and a logical line of reasoning a reader can follow without you being there to explain it.

It measures whether someone else — not you — could follow your solution from start to finish. That means correct notation, labelled diagrams and graphs, consistent units, and a logical sequence of steps, not just a correct final answer sitting on its own.

Criterion C marks how you communicate your maths — language, layout, representations. Criterion D marks whether you can apply maths to a real-world context and interpret results sensibly. You can lose Criterion D marks for a weak real-life conclusion even if your Criterion C working is flawless.

Consistency across the whole task is what separates 7-8 from 5-6. Use correct notation every time, label every graph and diagram, explain each step in a short phrase rather than jumping straight to numbers, and finish with a clear final statement — not just a boxed answer.

The most common one I see marking mocks: students write the correct final answer but skip the explanatory steps, so the reasoning isn't visible. Unlabelled axes, missing units, and switching between decimals and fractions without saying why also cost marks in every band above 3-4.

Not full essay-style sentences, but yes — short explanatory phrases matter. "Substitute x = 3 into the equation" tells a marker exactly what you did; a bare line of numbers doesn't. One clear phrase per step is usually enough to hit the top descriptor band.

Enough that a reader can rebuild your answer without a calculator or guesswork. For multi-step problems, show every algebraic manipulation and any substitution; for graphical tasks, label scale, axes and key points. Skipping steps to save time is the single biggest reason strong students miss level 7-8.

Not every single assessment — but across the year, your teacher needs at least one Criterion C-focused task per reporting period to award a final grade. In practice, most substantial investigations, projects and tests include a Criterion C component alongside A, B or D.

Command terms like "show that," "justify," "explain" and "hence" all signal that Criterion C is in play — they require you to demonstrate reasoning, not just state a result. "Calculate" alone can sometimes be answer-only, but pairing it with "show your method" pulls Criterion C back in.

MYP Criterion C is a standalone criterion marked out of 8 with published level descriptors. In DP Mathematics AA and AI, communication isn't a separate criterion — it's folded into the internal assessment's "presentation" and "communication" marking criteria, worth fewer marks overall but assessed similarly: clarity, notation, logical structure.

The fastest improvement I see comes from parents asking their child to explain a solved homework problem out loud, step by step, as if teaching a younger sibling. If your child stumbles explaining a step, that's exactly the gap a marker would also flag on paper — worth practising before the next assessment.

Yes — practising with real MYP-style tasks that include explicit Criterion C marking guidance is more useful than generic worksheets, since your child needs to see exactly what a level 7-8 explanation looks like versus a level 3-4 one. On RevisionPrep, MYP Mathematics Topical Worksheets and Revision Notes are built around these four criteria.