Algebra 2 (1st Edition)

Published by McDougal Littell
ISBN 10: 0618595414
ISBN 13: 978-0-61859-541-9

Chapter 10 Counting Methods and Probability - 10.2 Use Combinations and the Binomial Theorem - Guided Practice for Examples 1, 2, and 3 - Page 691: 3

Answer

21

Work Step by Step

We know the following equation for combinations: $$nC_r = \frac{n!}{(n-r)!\cdot r!}$$ Thus, we find: $$\frac{7!}{2!\left(7-2\right)!}\\ 21$$
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