Results 1 to 6 of 6

Math Help - Matrices and permutations

  1. #1
    Junior Member doomgaze's Avatar
    Joined
    Apr 2009
    Posts
    37

    Matrices and permutations

    I've been going over some review for some placement test I have to take, I've never done anything with Matrices (I think that's the plural for Matrix, haha) and I'm ruuuuusty on solving permutations:


    I don't think these are particularly difficult, I'm just slow in the subjects..Thanks for anyone who can clarify
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor harish21's Avatar
    Joined
    Feb 2010
    From
    Dirty South
    Posts
    1,036
    Thanks
    10
    Quote Originally Posted by doomgaze View Post
    I've been going over some review for some placement test I have to take, I've never done anything with Matrices (I think that's the plural for Matrix, haha) and I'm ruuuuusty on solving permutations:


    I don't think these are particularly difficult, I'm just slow in the subjects..Thanks for anyone who can clarify
    |A| means the determinant of a matrix. For a 2x2 matrix, that is a matrix with 2 rows and 2 columns:
    \left[\begin{array}{cc}a&b\\c&d\end{array}\right]

    the determinant is |A| = ad-bc.

    And if the determinant is zero, the matrix does not have an inverse.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    MHF Contributor harish21's Avatar
    Joined
    Feb 2010
    From
    Dirty South
    Posts
    1,036
    Thanks
    10
    (34) if you are considering the ways in which the committee of 3 people is chosen without order


    7C3 = \frac{7!}{3!(7-3)!} = \frac{7!}{3! \times 4!}
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Junior Member doomgaze's Avatar
    Joined
    Apr 2009
    Posts
    37
    Quote Originally Posted by harish21 View Post
    (34) if you are considering the ways in which the committee of 3 people is chosen without order


    7C3 = \frac{7!}{3!(7-3)!} = \frac{7!}{3! \times 4!}
    so you take the total amount of people then divide (total - the # of people per group) ?
    Follow Math Help Forum on Facebook and Google+

  5. #5
    MHF Contributor harish21's Avatar
    Joined
    Feb 2010
    From
    Dirty South
    Posts
    1,036
    Thanks
    10
    Quote Originally Posted by doomgaze View Post
    so you take the total amount of people then divide (total - the # of people per group) ?
    We are NOT taking the total amount/number of people here. The exclamation mark ! that you see after the numbers is called factorial.

    7!= 1*2*3....*7
    3!= 1*2*3
    4!= 1*2*3*4


    To know how this formula comes, you need to study permutations and combinations..Google it.

    This link might be useful
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Junior Member doomgaze's Avatar
    Joined
    Apr 2009
    Posts
    37
    Quote Originally Posted by harish21 View Post
    We are NOT taking the total amount/number of people here. The exclamation mark ! that you see after the numbers is called factorial.

    7!= 1*2*3....*7
    3!= 1*2*3
    4!= 1*2*3*4


    To know how this formula comes, you need to study permutations and combinations..Google it.

    This link might be useful
    Yeah I knew they were factorials, I guess I just didn't express it when I was trying to explain what I thought you said.

    Thanks for the link, it is clearing things up.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 1
    Last Post: August 29th 2011, 06:49 PM
  2. Replies: 2
    Last Post: November 25th 2010, 06:34 PM
  3. Permutations Matrices Question
    Posted in the Advanced Algebra Forum
    Replies: 3
    Last Post: September 24th 2010, 05:08 AM
  4. Total matrices and Commutative matrices in GL(r,Zn)
    Posted in the Advanced Algebra Forum
    Replies: 8
    Last Post: August 16th 2010, 02:11 AM
  5. Matrices represented by Symmetric/Skew Symmetric Matrices
    Posted in the Advanced Algebra Forum
    Replies: 7
    Last Post: October 25th 2008, 05:06 PM

Search Tags


/mathhelpforum @mathhelpforum