1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Intro Statistics combination/probability problems.

  1. Feb 23, 2012 #1
    Hello. Am I counting right with these problems? I can't remember exactly how they were worded, but I remember what they were asking...

    1) Given 20 men and 20 women, how many groups of 12 can you make with 6 men and 6 women.

    I said 20.Combination.6 * 20.Combination.6.

    2) given S= {1, 2, 4, 5, 7}, you will choose 3 randomly from the set. What's the probability of getting an even number greater than 500?

    I said 12 / 5.Permutation.3.

    How I got 12:

    1. 3 ways of having 5 first, 2 last.
    2. 3 ways of having 5 first, 4 last.
    3. 3 ways of having 7 first, 2 last.
    4. 3 ways of having 7 first, 4 last.

    Added it up to get 12. I then divided it by a permutation because order is important?...


    3) What is the probability that two randomly chosen people were both not born in June?

    I said P(First not born in June ^ Second not born in June)= (11/12) * (11/12)



    Is my counting right? Thanks for your help.
     
  2. jcsd
  3. Feb 23, 2012 #2

    Ray Vickson

    User Avatar
    Science Advisor
    Homework Helper

    You counting for (2) is incorrect. If you first pick 5, then picking any two other numbers gives you a result > 500. If you first pick 7, then picking any two other numbers gives you a result > 500. If you pick anything other than 5 or 7 first you will not get a result > 500.

    RGV
     
  4. Feb 24, 2012 #3
    @Ray Vickson,

    Thanks for your help.

    For number 2, they have to be even and >500, how do I go about solving that part?
     
  5. Feb 24, 2012 #4

    Ray Vickson

    User Avatar
    Science Advisor
    Homework Helper

    Surely you know what an even number looks like!

    RGV
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Intro Statistics combination/probability problems.
Loading...