in how many ways can 7 out of 21 students catch the flu
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Combinations. $\displaystyle {21 \choose 7} = \frac {21!} {(7!)(14!)}$
Originally Posted by aymers14 in how many ways can 7 out of 21 students catch the flu Only 1 way....when each of the 7 come into contact with the flu virus.
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