Results 1 to 3 of 3

Math Help - Permutation & Combination help.

  1. #1
    Newbie
    Joined
    Apr 2010
    Posts
    9

    Post Permutation & Combination help.

    1. Given the diagram below, determine the number of pathways starting from A and moving to B along the gridlines if a pathway must always move closer to B.

    Permutation & Combination help.-pathways_03_hole.png


    2. Given the diagram below, determine the number of pathways starting from A and moving to B along the gridlines if a pathway must always move closer to B.

    Permutation & Combination help.-7-4_quiz_complexpathways_c_cbel.png



    Please help me with these questions I do not know how to do it.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Opalg's Avatar
    Joined
    Aug 2007
    From
    Leeds, UK
    Posts
    4,041
    Thanks
    7
    Quote Originally Posted by danield3 View Post
    1. Given the diagram below, determine the number of pathways starting from A and moving to B along the gridlines if a pathway must always move closer to B.
    Starting from B, and working upwards and to the left, label each node with the number of paths from there to B.

    For the nodes immediately to the left of B, and also for those immediately above B, there is only one available path to B. For each other node, the number of paths from that node is the sum of the numbers for the nodes next to it on the right and below. Working all the way back to the node at A, you get the answer 34 for the total number of paths.

    Use the same method for the other part of the question.
    Attached Thumbnails Attached Thumbnails Permutation & Combination help.-combinations.png  
    Follow Math Help Forum on Facebook and Google+

  3. #3
    MHF Contributor
    Joined
    Dec 2009
    Posts
    3,120
    Thanks
    1
    Quote Originally Posted by danield3 View Post
    1. Given the diagram below, determine the number of pathways starting from A and moving to B along the gridlines if a pathway must always move closer to B.

    Click image for larger version. 

Name:	pathways_03_hole.png 
Views:	102 
Size:	1.8 KB 
ID:	17006


    2. Given the diagram below, determine the number of pathways starting from A and moving to B along the gridlines if a pathway must always move closer to B.

    Click image for larger version. 

Name:	7-4_quiz_complexpathways_c_cbel.png 
Views:	102 
Size:	1.7 KB 
ID:	17007



    Please help me with these questions I do not know how to do it.
    Hi danield3,

    here's another way..

    In part 1, the diagram is symmetrical.
    If we find the number of ways to go from A to C
    and the number of ways to go from C to B,
    given the directional restriction,
    we can multiply these to find the number of ways that require at least one internal path,
    in going through C.
    Add the external path.
    The exact same number of ways are available in going across the top first.

    In part 2, the ways can be summed independently from A to B through C,
    A to B through D while avoiding E, and A to B through E avoiding D.
    Attached Thumbnails Attached Thumbnails Permutation & Combination help.-grid1.jpg   Permutation & Combination help.-grid2.jpg   Permutation & Combination help.-grid3.jpg   Permutation & Combination help.-grid4.jpg  
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Permutation vs Combination
    Posted in the Discrete Math Forum
    Replies: 2
    Last Post: September 26th 2009, 03:18 PM
  2. Permutation/combination?
    Posted in the Statistics Forum
    Replies: 2
    Last Post: March 28th 2009, 09:45 AM
  3. Permutation or Combination?
    Posted in the Statistics Forum
    Replies: 1
    Last Post: November 16th 2008, 11:33 AM
  4. combination/permutation
    Posted in the Discrete Math Forum
    Replies: 0
    Last Post: October 17th 2008, 12:40 AM
  5. Permutation and Combination Help!
    Posted in the Statistics Forum
    Replies: 6
    Last Post: March 18th 2008, 01:21 PM

Search Tags


/mathhelpforum @mathhelpforum