Question

The library is to be given 3 books as a gift. The books will be selected from a list of 18 titles. If each book selected must have a different title, how many possible selections are there?

Answer 1

`((18),(3))=(18!)/((3!)(15!))=(18xx17xx16)/6=816`

Explanation:

We don't care in what order the books are selected, and so this is a combination problem.

`C_(n,k)=((n),(k))=(n!)/((k!)(n-k)!)` with `n="population", k="picks"`

`C_(18,3)=((18),(3))=(18!)/((3!)(15!))=(18xx17xx16)/6=816`