Originally Posted by

**adkinsjr** *Say I have 6 blue coins, 8 green coins, and 4 red coins, what is the probability that I will draw at random a blue, then a green, then another blue in that order? ....*

So basically from what I've read you can have combinations or permutations, permutations are "orderly" combinations.

Permutation with repetition where (order matters): $\displaystyle _nP_r=n^r$

Permutation without repetition (order matters): $\displaystyle _nP_r= \frac{n!}{(n-r)!}$

Combination with repetition (order doesn't matter): $\displaystyle _nC_r=\frac{n!}{(n-r)!r!}$

Combination without repetition (order doesn’t matter):$\displaystyle _nC_r=\frac{(n+r-1)!}{r!(n-1)!}$

Where $\displaystyle n$ is the number of things, and $\displaystyle r$ is the number of things being used.

Maybe I'm confusing the meaning of "repetition" here. Maybe that does not mean repetition as in the same "type" of coin appearing more than once in a certain permutation, but the repetition of a permutation itself i.e. drawing blue-red-blue could happen more than once.