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Combinatorics 1
Multiplication Principle
If there are m ways of performing 1 task and n ways of performing another task, then there are $m \times n$ ways of performing both tasks.
Addition Principle
If there are m ways of performing a specific task, and there are n ways of performing the same task but in another way, then there are $m+n$ ways of completing the tasks.
Permutations
- A permutation is an ordered arrangement of a set of objects
- When we arrange r objects from a total set of n objects the total number of possible arrangements is given by:
$$nPr = \frac{n!}{(n-r)!}
$$
