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Discrete-Math · Counting

7 choose 2

7,\ 2

Step by step

  1. \binom{7}{2} = \frac{7!}{2!\,(7-2)!}

    Unordered selections: n! / (k! (n−k)!).

  2. = \frac{5040}{2 \times 120} = 21

Reveal the answer
\binom{7}{2} = 21