math 4th qe def

 arrangement of objects in a specific order. The order of the arrangement is significant.

P(n, r) = n!/(n-r)!

P(n) = n! 

P(n, r) = n!/(n-r)! or nPr

P= n!/p!q!r!

P=(n-1)! 

With repetition (identical objects), divide by factorials of [] objects.

Circular permutations reduce by 1! because rotation doesn't change []

a selection of objects where the order does not matter.

C(n, r)= n!/r!(n-r)!