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Math Help - Don't know where to start...

  1. #1
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    Don't know where to start...

    This problem seemed so simple in the beginning, but now, I am completely confused. I don't even know where to start. Is it just me?

    4. In a class of 25 students, there are 13 boys and 12 girls. A committee of 3 students is needed and is to be chosen randomly from the group of 25.
    a. What is the probability of the group will have 2 boys and 1 girl?
    b. What is the probability of the group having all boys or all girls?
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by vedmachka View Post
    This problem seemed so simple in the beginning, but now, I am completely confused. I don't even know where to start. Is it just me?

    4. In a class of 25 students, there are 13 boys and 12 girls. A committee of 3 students is needed and is to be chosen randomly from the group of 25.
    a. What is the probability of the group will have 2 boys and 1 girl?
    this is

    \frac {\text{the total number of (distinct) groups you can form with 2 boys and 1 girl}}{\text{total number of groups of size three}}

    hint: think "combinations"



    b. What is the probability of the group having all boys or all girls?[/FONT][/LEFT]
    this is P(\text{all boys}) + P(\text{all girls})

    where P(\text{all boys}) = \frac {\text{total number of (distinct) groups with 3 boys and no girls}}{\text{total number of groups of size 3}}

    and

    P(\text{all girls}) = \frac {\text{total number of (distinct) groups with 3 girls and no boys}}{\text{total number of groups of size 3}}


    hint: the same as in the last problem
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