Most IB Mathematics students spend hundreds of hours preparing for their exams. Very few spend any time understanding how their paper is actually marked — and that's a missed opportunity, because understanding how examiners think changes how you write your answers.
Here's what actually happens on the other side of the table, from someone who has been there.
Every mark has a type
When an IB examiner marks your paper, they are not simply deciding whether your answer is right or wrong. They are awarding specific types of marks, each with its own rules.
Awarded for demonstrating the correct mathematical method, even if your final answer is wrong. If you set up the problem correctly, showed the right approach, and made a small arithmetic error along the way, you can still earn the M mark.
Awarded for correct answers, and usually dependent on the M mark being awarded first. In most cases, if you didn't show the method, you can't earn the accuracy mark — even if your answer is correct.
These appear most often in questions that ask you to justify, explain, or prove something. A correct conclusion without a clear reason will not earn an R mark. These are the marks students most commonly lose without realising it.
In "show that" questions, the final answer is printed in the question. The examiner is not marking your answer — they're marking your working. Every step must be shown explicitly and logically. Skipping steps, even obvious ones, costs marks.
The follow-through rule
One of the most important — and most misunderstood — rules in IB marking is follow-through.
If you make an error in part (a) and carry that incorrect answer into part (b), the examiner can still award you marks in part (b), as long as your method in part (b) is correct given your answer from part (a).
This means two things for you as a student. First, never leave a part blank just because you got the previous part wrong. Second, always show your working clearly enough that the examiner can see you applied the right method — even with the wrong number.
Follow-through marking exists to reward mathematical understanding, not just correct arithmetic. Use it to your advantage. This is especially important in Paper 3, where investigations have many connected parts. For more, read our full Paper 3 guide.
What "hence" actually means
When a question says "hence find..." it is not a suggestion. It is an instruction.
"Hence" means you must use the result from the previous part to answer the current part. If you ignore it and solve the problem using a different method — even if your answer is correct — you will not earn the method marks.
This is one of the most consistent sources of lost marks I saw as an examiner. Students would produce a perfectly correct answer using an alternative method, not realising they had answered a different question from the one being asked.
If the question says "hence or otherwise", you have a choice. If it says "hence" alone, you do not.
How examiners handle borderline working
Examiners are trained to award marks wherever they legitimately can. The IB marking philosophy is to look for evidence that the student understands the mathematics — not to deduct marks.
What this means in practice: if your working is messy but the mathematics is sound, an examiner will follow it carefully and award every mark they can. If your working is unclear, contradictory, or missing, the examiner has nothing to follow — and marks cannot be awarded for work that isn't there.
Write for the examiner, not for yourself. Your working should tell a clear, logical story from the question to the answer.
The most common reasons marks are lost
After marking hundreds of scripts, these are the patterns I saw most consistently:
No working shown. A correct answer with no working earns the accuracy mark but loses the method mark. In a four-mark question, that could mean earning one mark out of four.
Premature rounding. If you round an intermediate answer and carry that rounded value forward, your final answer may be outside the accepted range. Keep full calculator values until the very last step.
Ignoring command terms. "Write down," "find," "show that," "hence," "justify" — each of these tells you exactly what the examiner expects. Students who ignore them answer a different question from the one being marked.
Incomplete conclusions. In questions that ask you to make a decision or justify a result, the final statement matters. A correct calculation followed by no conclusion often loses the last mark.
Crossed out working. If you cross out working, the examiner cannot mark it — even if it was correct. As an examiner, I always faced this moral dilemma, but I simply cannot award marks for crossed-out work. Only cross out work you are certain is wrong.
What this means for how you prepare
Understanding how your paper is marked should change how you practise. When you review past papers, don't just check whether your final answer matches. Check whether your working would earn every available mark — the method marks, the accuracy marks, and the reasoning marks.
Ask yourself: if an examiner read only my working, with no context, could they follow my reasoning and award me every mark I deserve?
That question is worth asking after every practice paper you do.
Practise answering the way examiners expect.
HAN is trained on exactly this kind of examiner logic — free, available anytime, and built on 20+ years of IB marking experience.
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