Permutations and Combinations

5P2=120

5C2=10


This week we learned about permutations and combinations.  Permutations mean important or considered and combinations mean not important or not considered.  There are two separate formulas for permutations and combinations.  The permutation formula is nPr= n!/(n-r)! and the combination formula is nCr= n!/(n-r)! r!.  Basically all you have to do to solve these types of problems is just to plug it into the formula you are given.  So for the first example I did, the 5 in the n in this problem and the 2 is the r in this problem.  You are given that it is permutation so you know to use that formula.  So you would do 5!/3! and your answer is 120.  For the second example I did, the 5 in this problem is the n and the 2 in the problem is the r.  It is the same numbers, but you have to use the other formula since you are told it is combination.  When you use this formula, you get 5!/3!2! and the equals 10.