Algorithm with Math It is important to have a strategy in order to understand and solve problems. It is necessary to understand the greatest common divisor, least common multiple, permutation, combination, and power set. permutations and combinations Selecting and listing only a subset of n is called a permutation. Permutations must be listed in order. formula: nPr = n! / (n-r)! > Caution: 0! and 1! is 1 In combinations, groups are more important than