Counting
Use the multiplication rule, permutations and combinations.
The rules
- Multiplication rule: multiply the choices at each step.
- Order matters (permutation): n!/(n − r)!.
- Order doesn't matter (combination): n!/(r!(n − r)!).
- A committee is a combination. A line-up is a permutation.
Watch out: Using permutations when order doesn't matter.
Worked example
How many ways can you choose a committee of 3 from 8 people?
- Order doesn't matter, so use C(8, 3).
- 8·7·6 / 6 = 56.
Answer: 56
Try it yourself
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