## Algebra 1: Common Core (15th Edition)

Published by Prentice Hall

# Chapter 12 - Data Analysis and Probability - 12-6 Permutations and Combinations - Practice and Problem-Solving Exercises - Page 766: 34

21

#### Work Step by Step

We know that: $_nC_r =\frac{_nP_r}{r!} = \frac{n!}{(n-r)!r!}$ $_7C_5 = \frac{7!}{(7-5)!5!}$ $\frac{ 7!}{5!2!}$ We also know that: $x! = x(x-1)(x-2)...(1)$ Thus, we have: 21

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