Question

In how many ways can you arrange six out of eight books on a shelf?

Answer 1

I hope I am correct! 28 ways

Explanation:

This is a permutation question

The number of arrangements is `(n!)/((n-r)!r!)`

where
`n=8`
`r=6`

Giving
`color(brown)((n!)/((n-r)!r!))" "->" " color(blue)(( 8!)/((8-6)!6!)`

Always look for factorials that can be cancelled.

`" "(8xx7xxcancel(6!))/((2xx1)xxcancel(6!) )`

`" "4xx7 = 28`