Here's the question you clicked on:
Chelsea04
can someone remind me what the formula is for nPr and nCr?
\[nPr = \dfrac{n!}{(n - r)!} \ \ \ \ \quad nCr = \dfrac{n!}{(n - r)!r!}\]
Where \(n! = n \times (n - 1) \times (n - 2) \cdots 1\)
oh right...my mind just blanked... Thank you @ParthKohli
For example:\[9C4 = \dfrac{9!}{(9 - 4)!4!} = \dfrac{9!}{5!4!} = \dfrac{9 \times 8 \times 7 \times 6}{4 \times 3 \times 2}\]