Question 146144
{{{P[n,r]=n!/(n-r)!}}} where {{{n!=n*(n-1)*(n-2)}}}...{{{3*2*1}}}


Example:  Permutations of 6 things taken 4 at a time.  {{{P[6,4]=6!/(6-4)!=(6*5*4*3*2*1)/(2*1)=720/2=360}}}