Question 942850
the permutation of n things taken x at a time is equal to n! / (n-x)!


for example:


if n = 3 and x = 2, then the permutation of 3 things taken 2 at a time is equal to 3! / 1! which is equal to 3! which is equal to 3*2 = 6.


if n = 3 and x = 1, then the permutation of 3 things taken 1 at a time is equal to 3! / 2! which is equal to 3.


the permutation of n things taken n at a time is always n!.


for example:


if n = 3 and x = 3, then the permutation of 3 things taken 3 at a time is equal to 3! / 0! which is equal to 3!.


0! is always equal to 1.