Thinking Mathematically (6th Edition)

Published by Pearson
ISBN 10: 0321867327
ISBN 13: 978-0-32186-732-2

Chapter 11 - Counting Methods and Probability Theory - 11.2 Permutations - Concept and Vocabulary Check: 2

Answer

$\displaystyle \frac{n!}{(n-r)!}$

Work Step by Step

See: Permutations Formula, page 698. The number of permutations possible if $r$ items are taken from $n$ items is ${}_{n}P_{r}=\displaystyle \frac{n!}{(n-r)!}$. ( $n!=n(n-1)(n-2)\cdots(3)(2)(1)$ )
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