How to Approach Section B Questions in IB Math

If you've sat a past paper, you already know that Section B feels different from Section A. The questions are longer, the marks are higher, and the path to a full score is less obvious.

Many students lose a disproportionate number of marks in Section B — not because the mathematics is harder, but because they don't approach it differently from Section A. It should be approached differently.

Here is how.

What is Section B?

In IB Mathematics Papers 1 and 2, questions are divided into two sections:

Section A contains shorter questions, typically worth 4–8 marks each, covering a range of topics. Each question is largely self-contained.

Section B contains longer questions, typically worth 12–20 marks each, with multiple connected parts. Each succeeding part usually depends on or connects to the parts before it.

Understanding this structure changes how you should read, plan, and answer Section B questions.

Read the whole question first

Before attempting part (a), read every part of the Section B question from beginning to end.

This is strategically important. Section B questions are designed so that later parts connect to earlier ones. Reading ahead tells you what part (a) is building towards, which helps you understand what level of detail and what form of answer is expected.

Students who jump straight into part (a) without reading ahead often find themselves having to redo their working when they reach part (c) and realise they needed a different form of the answer.

Use the mark allocation as a guide

The marks allocated to each part tell you how much work is expected.

A one-mark part requires one clear step or statement. A five-mark part requires a complete method with multiple steps. If you've answered a five-mark question in two lines, you almost certainly haven't shown enough working.

Check the mark allocation before you start each part and calibrate your response accordingly.

Show full working on every part

In Section A, some students get away with minimal working because the questions are short and the answer is quickly verifiable. In Section B, this approach is costly.

Section B questions carry more marks, and more of those marks are method marks. A correct final answer with no working in a ten-mark Section B question might earn you two marks out of ten. Full working, even if it contains a small error, might earn you more marks than a correct answer with no working.

Write every step. Show every method. Leave nothing for the examiner to infer. Examiners want to award marks, not to deduct marks.

Never abandon a Section B question

This is the most important rule for Section B.

If you get stuck on part (c), do not leave parts (d), (e), and (f) blank. Move forward. Attempt every part, even if you have to use an assumed or incorrect answer from the previous part.

Something is always better than nothing.

Manage your time across Section B

Section B questions are long, and it is easy to spend too much time on one question at the expense of the others.

A rough guide: divide the marks available in Section B by the time available for that section, and allocate time per mark accordingly. If you are spending significantly more than this on any single part, move on and come back if time allows.

Students who run out of time before attempting the final Section B question lose all of those marks. Students who manage time well and attempt every question, even imperfectly, almost always score higher.

A note on "show that" parts in Section B

Section B questions frequently include "show that" parts, often early in the question. These are worth paying careful attention to — not rushing through.

The reason they appear early is that the result you are asked to show is almost always used in a later part. If you skip steps in the "show that" and arrive at the answer given, you may not have earned full marks — and more importantly, you may not fully understand the result well enough to use it correctly later.

Slow down on "show that" parts. Show every step. It pays dividends in the parts that follow.

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