Question

In Permutations:
what is the difference between P= n! / (n-r)!r!
And C=n!/(n-r)! ???????

Answer 1

@ganeshie8 help plz

Answer 2

Permutation counts order.

Combination does not.

For ex:
AB is consider different from BA in permutation, whereas AB and BA are the same in combination

Answer 3

As another example, consider the possible strings of three different letters, \(a,b,c\):
\[\begin{matrix}\color{red}{abc}&\color{blue}{bac}&\color{blue}{cab}\\
\color{green}{acb}&\color{green}{bca}&\color{red}{cba}
\end{matrix}\]
The total number of permutations (in which order matters) is 6.

The total number of combinations (in which order doesn't matter) is 3 (indicated by the three pairs of color-coded strings).