Answer
120 arrangements
Work Step by Step
In the first place any of the 5 books can be placed, but in the second place we can only choose one from the $4$remaining books. The number of choices for the next place will also be one less than the previous one.
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Thus, this involves a permutation where $n=5$ and $r =5$.
Using the formula $P(n,n) = n!$ gives:
$P(5,5) = 5! = 5(4)(3)(2)(1)=120$
