Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Simple problem involving permutations

  1. Mar 5, 2013 #1
    Hi, here's the question, I just need someone to confirm that I'm doing it right (been a while since my last stat class):

    Let's say I have 30 balls all of different colors. I want to know in how many different ways I can align 5 balls picked at random (thus ordering matters). Note that one must be blue, one red and one yellow.

    So let's start with the blue one. I have 5 different ways to arrange it (either place it first in line, or second, or third etc.). Then let's say I'm looking a the red one: I have 4 ways left to arrange it. Finally I have 3 slots left for the yellow one. Now for the remaining 2 balls, I still have 27 balls to choose from.

    Would the answer be 5*4*3*(27 Permute 2)?

    Thanks.
     
  2. jcsd
  3. Mar 5, 2013 #2

    chiro

    User Avatar
    Science Advisor

    Hey erogard.

    That looks right to me.

    Also if you want to test things like this, what I recommend you do is simulate the stochastic process in a computer package like R and then look at the probability of the event happening over say 10,000 or 100,000 iterations (which is quick with modern day computers).

    This is always a good way for you to independently verify your own work.
     
  4. Mar 22, 2013 #3
    How many balls are blue, red, and yellow within the 30 balls?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Simple problem involving permutations
  1. Permutations problem (Replies: 1)

  2. Simple permutation (Replies: 2)

Loading...