## Thinking Mathematically (6th Edition)

$76,904,685$ ways
The order in which the books are chosen is not important. Combinations, ${}_{n}C_{r}=\displaystyle \frac{n!}{(n-r)!r!}$ ${}_{40}C_{8}=\displaystyle \frac{40!}{(40-8)!8!}$ $=\displaystyle \frac{40\times 39\times 38\times 37\times 36\times 35\times 34\times 33}{1\times 2\times 3\times 4\times 5\times 6\times 7\times 8}$ $=\displaystyle \frac{1\times 39\times 19\times 37\times 1\times 5\times 17\times 33}{1\times 1\times 1\times 1\times 1\times 1\times 1\times 1}$ $= 76,904,685$