## Thinking Mathematically (6th Edition)

Published by Pearson

# Chapter 11 - Counting Methods and Probability Theory - 11.3 Combinations - Exercise Set 11.3 - Page 707: 8

210

#### Work Step by Step

The number of possible combinations if r items are taken from n items is nCr = $\frac{n!}{r!(n-r)!}$ 10C6 = $\frac{10!}{6!(10-6)!}$ =$\frac{10!}{6!4!}$ =$\frac{10*9*8*7*6!}{6!4!}$ =$\frac{10*9*8*7}{4*3*2*1}$ = 210

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