If the order doesn't matter, it is a Combination.
If the order does matter, it is a Permutation. (To help you to remember, think "Permutation" as "Position".)
How many ways are there to choose r elements from a set of n elements?
|Order Matters||Order Does Not Matter|
|Repetition Is Allowed||nr||C(n+r-1, r) =
|The number of ways to fill r slots from n catgories with repetition allowed.|
|Repetition Is Not Allowed||P(n,r)||C(n,r)|
P(n,r) = n! / (n-r)!
C(n,r) = n! / r!(n-r)!
How many ways can I select 12 cans of soda from a cooler containing large quantities of Coke, Pepsi, Diet Coke, Root Beer and Sprite? ___________