Question

Evaluate 11P4?

Answer 1

`=11*10*9*8` which equals to:
`7920`

Explanation:

The formula for permutations is:
`P(n,r)=(n!)/((n−r))!` or in this form
`=_nP_r=(n!)/((n−r)!)`. Using the givens we know:
`n=11` and `r=4`. Inputting values:
`=_(11)P_4=(11!)/((11−4)!)` Simplifying:
`=_(11)P_4=(11!)/(7!)` Since `7! =7*6*5...` and `11! =11*10...*7*6*5...` we can cancel out the factors from 7 on down to get:
`=11*10*9*8` which equals to:
`7920`
Source (I forgot equation)