Counting: Disposition, Permutations and Combinations
Combinatorics is "The FIne Art of Counting". Coutnign what? Counting elements from one or more sets.
Fundamental Principle of Counting (Combinatorics)
If something can be chosen, or can happen, or be done, in n different ways, and, after that has happened, something else can be chosen in p different ways, then the number of ways of choosing both of them is n*p.
