SOLUTION: A class contains 9 boys and 3 girls. In how many ways can a committee of 4 students be formed if the committee must contain at least one girl?

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Question 1092067: A class contains 9 boys and 3 girls. In how many ways can a committee of 4 students be formed if the committee must contain at least one girl?
Answer by greenestamps(13198) About Me  (Show Source):
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The total number of ways of forming a committee of 4 from 12 students is "12 choose 4", which is
C%2812%2C4%29+=+%2812%21%29%2F%28%288%21%29%284%21%29%29+=+495

The number of ways of forming the committee with only boys is "9 choose 4",
C%289%2C4%29+=+%289%21%29%2F%28%285%21%29%284%21%29%29+=+126

So the number of ways of forming the committee with at least one girl is 495-126=369.