Solve the problem.
-The library is to be given 5 books as a gift. The books will be selected from a list of 21 titles. If each book selected must have a different title, how many possible selections are there?

Question

Quizplus · Accepted Answer

This is a combination problem, not a permutation, because the order in which the books are selected does not matter. The formula for combinations is C(n, k) = n! / [k!(n-k)!], where n is the total number of items to choose from, k is the number of items to choose, and "!" denotes factorial, the product of all positive integers up to that number. Here, n=21 (the total number of books) and k=5 (the number of books to select). Thus, C(21, 5) = 21! / [5!(21-5)!] = 20,349.

Solve the Problem. -The Library Is to Be Given 5 Books as a Books