Probability

Combinations C(n,r)

Compute C(n,r) = n! / (r!(n−r)!) — the number of unordered selections of r items from n. See how C(n,r) = P(n,r) / r! and why order doesn't matter in combinations.

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Step-by-Step Work

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P(n,r) → ÷ r! → C(n,r)