The time traveler can choose 3 books with him, but he can only take 57.
So in this case the order doesn't matter, therefore, we are going to use a combination:
Use the combination formula:
[tex]C\text{ =}\frac{n!}{r!(n-r)!}[/tex]When n is the total of books and r the sample.
n = 57 and n =3
Replace these values on the formula:
[tex]C=\frac{57!}{3!(57-3)!}=\frac{57!}{3!54!}=29260[/tex]Hence, there are 29260 ways that the books can be selected.
