Results 1 to 2 of 2

Math Help - Probability Q

  1. #1
    Junior Member
    Joined
    Dec 2009
    Posts
    61

    Probability Q

    Hi I need help with this question
    3 chidlren are chosen at random from 9 girls and 3 boys. What is the probability that
    i. at least one boy is chosen?
    ii. more girls than boys are chosen?

    I've got that the possible outcomes is 55 but I dont know what to do next.
    Thanks.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    Dec 2009
    Posts
    3,120
    Thanks
    1
    Quote Originally Posted by Detanon View Post
    Hi I need help with this question
    3 chidlren are chosen at random from 9 girls and 3 boys. What is the probability that
    i. at least one boy is chosen?
    ii. more girls than boys are chosen?

    I've got that the possible outcomes is 55 but I dont know what to do next.
    Thanks.
    (i)

    At least 1 boy means "more than no boys"

    P(no\ boys)=\frac{\binom{9}{3}}{\binom{12}{3}}

    which is the probability all 3 are girls.
    Select 3 girls from 9, divide by the selections of 3 children from 12.

    then subtract this from 1.

    (ii)

    more girls than boys means 3 girls or 2 girls with 1 boy

    \frac{\binom{9}{3}+\binom{9}{2}\binom{3}{1}}{\bino  m{12}{3}}
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 10
    Last Post: January 21st 2011, 11:47 AM
  2. Replies: 3
    Last Post: May 29th 2010, 07:29 AM
  3. Replies: 1
    Last Post: February 18th 2010, 01:54 AM
  4. Replies: 3
    Last Post: December 15th 2009, 06:30 AM
  5. Continuous probability - conditional probability
    Posted in the Statistics Forum
    Replies: 1
    Last Post: October 1st 2009, 01:21 AM

Search Tags


/mathhelpforum @mathhelpforum