Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

Published by Pearson
ISBN 10: 0-32193-104-1
ISBN 13: 978-0-32193-104-7

Chapter 12 - Counting and Probability - Section 12.2 Permutations and Combinations - 12.2 Assess Your Understanding - Page 875: 22



Work Step by Step

Recall: $C(n, r)=\dfrac{n!}{(n-r)!r!}$ ways. Thus, \begin{align*} C(18, 9)&=\dfrac{18!}{(18-9)!9!}\\ \\&=\dfrac{18!}{9!9!} \end{align*} Using a calculator gives $C(18, 9)=\dfrac{18!}{9!(18-9)!}=48,620$
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