# Chapter 12 - Counting and Probability - Section 12.2 Permutations and Combinations - 12.2 Assess Your Understanding - Page 874: 6

$C(n, r)=\dfrac{n!}{(n-r)!r!}$

#### Work Step by Step

If we want to arrange $r$ elements out of $n$ where order does not matter (which is called combination), not allowing repetition, we can do this in $C(n, k)=\dfrac{n!}{(n-r)!r!}$ different ways.

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