Chords

How many 4-tones chords (chord = at the same time sounding different tones) is possible to play within 7 tones?

Correct answer:

n =  35

Step-by-step explanation:

$n=C_4(7)=\left({\displaystyle \genfrac{}{}{0px}{}{7}{4}}\right)={\displaystyle \frac{7!}{4!(7-4)!}}={\displaystyle \frac{7\cdot 6\cdot 5}{3\cdot 2\cdot 1}}=35$

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