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NotesMath AA HLTopic 1.10Group selections & restrictions
Back to Math AA HL Topics
1.10.51 min read

Group selections & restrictions

IB Mathematics: Analysis and Approaches • Unit 1

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Contents

  • Exactly so many from each group
  • At least / at most
It's a committee → use C, not P: A committee/group has no order — {Ana, Ben} is the same committee as {Ben, Ana} — so you CHOOSE with ⁿCᵣ, never arrange with ⁿPᵣ. (Use P only when there are positions/ranks/roles.)

Need exactly so many from each type (say 2 men AND 2 women)? Choose from each group, then multiply (AND → ×).

IB-style question — exactly 2 men

A committee of 4 is chosen from 5 men and 6 women. It must contain exactly 2 men.

How many committees are possible?

Step by step

  1. The committee needs 2 men AND 2 women (that's 4). Choose the men.
  2. Choose the women.
  3. Each of the 10 ways to pick the men can pair with ANY of the 15 ways to pick the women — that's why 'AND' means multiply.

Final answer

150 committees.

[Diagram: math-choice-boxes] - Available in full study mode

Add the cases (or take away the unwanted): "At least 2 women" = exactly 2 + exactly 3 + … — add the cases.

If that's a lot of cases, do total − the unwanted instead.

IB-style question — at least 2 women

A team of 4 is chosen from 5 men and 6 women. It must contain at least 2 women.

How many teams?

Step by step

  1. Exactly 2 women (2W, 2M).
  2. Exactly 3 women (3W, 1M).
  3. Exactly 4 women (4W, 0M).
  4. Add the cases.

Final answer

265 teams.

Faster: count the opposite: Total minus the unwanted (0 or 1 woman):

¹¹C₄ − (⁵C₄ + ⁶C₁×⁵C₃) = 330 − (5 + 60) = 265 — same answer.

IB Exam Questions on Group selections & restrictions

Practice with IB-style questions filtered to Topic 1.10.5. Get instant AI feedback on every answer.

Practice Topic 1.10.5 QuestionsBrowse All Math AA HL Topics

How Group selections & restrictions Appears in IB Exams

Examiners use specific command terms when asking about this topic. Here's what to expect:

Define

Give the precise meaning of key terms related to Group selections & restrictions.

AO1
Describe

Give a detailed account of processes or features in Group selections & restrictions.

AO2
Explain

Give reasons WHY — cause and effect within Group selections & restrictions.

AO3
Evaluate

Weigh strengths AND limitations of approaches in Group selections & restrictions.

AO3
Discuss

Present arguments FOR and AGAINST with a balanced conclusion.

AO3

See the full IB Command Terms guide →

Related Math AA HL Topics

Continue learning with these related topics from the same unit:

1.1.1Writing standard form
1.1.2Standard form by hand
1.10.1Arrangements (order matters)
1.10.2Selections (order doesn't matter)
View all Math AA HL topics

Improve your exam technique

Command terms, paper structure, and mark-scheme tips for Math AA HL

Previous
1.10.4Required person / fixed member
Next
Together restrictions1.10.6

11 practice questions on Group selections & restrictions

Students who practiced this topic on Aimnova scored 82% on average. Try free practice questions and get instant AI feedback.

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