- #1

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*n*options and

*r*selections while repetition is allowed you are supposed to do (

*n+r*-

*1*)!

**/**

*r!*(

*n*-

*r*)! and the purpose of

*r*! as a denominator is to act as a ratio to eliminate same outcomes but of different orders and is what makes us calculate the combination instead of a permutation.

However why can I not simply remove the

*r*! to use it to calculate permutation? so: ( n+r-1 )! / ( n-r )!