1. Limited time only! Sign up for a free 30min personal 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!

Homework Help: Simple question 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)?

  2. jcsd
  3. Mar 5, 2013 #2

    Ray Vickson

    User Avatar
    Science Advisor
    Homework Helper

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted