Thinking Mathematically (6th Edition)

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

Chapter 11 - Counting Methods and Probability Theory - 11.3 Combinations - Exercise Set 11.3 - Page 707: 41


$360$ ways

Work Step by Step

In a race, the position of finishing matters, order matters, so this problem involves permutations. ${}_{n}P_{r}=\displaystyle \frac{n!}{(n-r)!}$ ${}_{6}P_{4}=\displaystyle \frac{6!}{(6-4)!}=6\times 5\times 4\times 3=360$
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