diff --git a/guide/english/mathematics/combinations-and-permutations/index.md b/guide/english/mathematics/combinations-and-permutations/index.md index 73086ca295..998a4ed838 100644 --- a/guide/english/mathematics/combinations-and-permutations/index.md +++ b/guide/english/mathematics/combinations-and-permutations/index.md @@ -10,19 +10,19 @@ title: Combinations and Permutations This is an example of a permutation. A permutation is the number of different ordered possibilities that can occur in a given situation. A permutation can be with or without repetition, as can a combination. If we say that there is a permutation for n things with r possibilities, the formulae will be: - #####**With Repetition:** - n^r +**With Repetition:** + - #####**Without Repetition:** - n\!/(n-r)\! +**Without Repetition:** + Returning to the problem at the top, what if they were sitting in three identical chairs instead of having rankings? This is an example of a combination. In a combination, order doesn't matter. Therefore, every permutation of the same combination has to be eliminated. This creates two more formulae: - #####**With Repetition:** - (r+n-1)\!/(r\!(n-1)\!) +**With Repetition:** + - #####**Without Repetition:** - n\!/(r\!(n-r)\!) +**Without Repetition:** + ###Sources