Practice variation 2 of 3
Combinatorics — A committee with a condition
Your question
Choose a committee of 4 from 9 people if two specified people cannot both serve.
This practice question was inspired by Question 13(b) in the 2025 NSW HSC Mathematics Extension 1 examination, © NESA. It is an original TestMum variation that practises the same mathematical idea, not an official NESA question.
Before you check
- Have you stated every choice or assumption?
- Can another student follow each line?
- Did you verify the final result independently?