C n r n r. N r. One could say that a permutation is an ordered combination.
Now this and my brain whenever I start to think in terms of permutations I actually think in these ways.
Combinations and Permutations Calculator. When order matters and repetition is allowed if n is the number of things to choose from balloons digits etc and you choose r of them 5 balloons for the party 4 digits for the password etc the number of permutations will equal P nr. N r. When p particular things are always included and q particular things are always excluded n-p-q C r-p.