Permutations and combinations the various ways in which objects from a set may be selected generally without replacement to form subsets. Combination refers to the mixture of n things taken k at a time without repetition. In order to determine the correct number of permutations we simply plug in our values into our formula.
Use permutations when order is necessary.
Combination refers to the mixture of n things taken k at a time without repetition. N P r n r. Permutations and combinations the various ways in which objects from a set may be selected generally without replacement to form subsets. This number will go in the denominator of our probability formula since it is the number of possible outcomes.