Results 1 to 2 of 2

Math Help - probability using permutations/combinations

  1. #1
    Newbie
    Joined
    Jul 2007
    Posts
    2

    probability using permutations/combinations

    A bag contains 4 red and 3 green blocks. 3 blocks are randomly selected from the bag. Determine the probability that all three are red given that

    i.) replacement occurs between the second and third selections

    ii.) no replacement occurs
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Super Member

    Joined
    May 2006
    From
    Lexington, MA (USA)
    Posts
    11,682
    Thanks
    614
    Hello, Sam!

    A bag contains 4 red and 3 green blocks.
    Three blocks are randomly selected from the bag.
    Determine the probability that all three are red given that:

    a) replacement occurs between the second and third selections
    First block is red: P(\text{\#1 red}) = \frac{4}{7}
    Second block is red: P(\text{\#2 red}) = \frac{3}{6} . . . . The second block replaced.
    Third block is red: P(\text{\#3 red}) = \frac{3}{6}

    Therefore: P(\text{3 red}) \;=\;\frac{4}{7}\cdot\frac{3}{6}\cdot\frac{3}{6} \;=\;\frac{1}{7}



    b) no replacement occurs
    First block is red: P(\text{\#1 red}) = \frac{4}{7}
    Second block is red: P(\text{\#2 red}) = \frac{3}{6}
    Third block is red: P(\text{\#3 red}) = \frac{2}{5}

    Therefore: P(\text{3 red}) \;=\;\frac{4}{7}\cdot\frac{3}{6}\cdot\frac{2}{5} \;=\;\frac{4}{35}

    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. probability combinations n permutations
    Posted in the Advanced Statistics Forum
    Replies: 1
    Last Post: April 12th 2010, 04:02 AM
  2. Probability Permutations and Combinations
    Posted in the Statistics Forum
    Replies: 6
    Last Post: August 26th 2009, 05:44 AM
  3. Factorials, Combinations, Permutations & Probability
    Posted in the Advanced Statistics Forum
    Replies: 3
    Last Post: April 7th 2009, 09:21 AM
  4. Permutations and Combinations in Probability
    Posted in the Statistics Forum
    Replies: 6
    Last Post: February 19th 2009, 01:21 PM
  5. Permutations &Combinations in Probability
    Posted in the Statistics Forum
    Replies: 1
    Last Post: February 18th 2009, 09:44 PM

Search Tags


/mathhelpforum @mathhelpforum