Question

NCr/nPr=r!
give proof.

Answer 1

That's not true. If
`n\mathrm Cr` and
`n\mathrm Pr` are defined as


`n\mathrm Cr=(n!)/(r!(n-r)!)`

`n\mathrm Pr=(n!)/((n-r)!)`

then


`(n\mathrm Cr)/(n\mathrm Pr)=((n!)/(r!(n-r)!))/((n!)/((n-r)!))=\frac1{r!}`