Just one sec...
Hey! Sign in to get help with your study questionsNew here? Join for free to post

Edexcel D2 Transportation Problem

Announcements Posted on
Take our short survey, £100 of Amazon vouchers to be won! 23-09-2016
    • Thread Starter
    Offline

    0
    ReputationRep:
    Hi, I am self-teaching D2 and am having trouble grasping how to obtain an improved solution using the stepping-stone method. The question gives a table of costs, and I have firstly used the north-west corner method of getting an initial solution. I have calculated improvement indices, but do not know how to pick a loop in order to improve my solution.

    The original question, and my initial solution are shown in the picture, and I have calculated improvement indices
    I 1,2 = 2
    I 1,3 = 0
    I 3,1 = -1
    I 3,2 = 2

    I'm slightly stuck how to carry on, and any help would be really great, thanks!
    Attached Images
     
    Offline

    2
    ReputationRep:
    The index on (3,1) is negative so you want to send goods along that route.

    Use the stepping stone method. There's only one possibility: in the initial solution, add x to box (3,1), subtract x from box (2,1), add x to box (2,3) and subtract x from box (3,3). Then pick x to be as large as possible so as to not make any of the boxes in the new solution negative. Then re-test for optimality.
    • Thread Starter
    Offline

    0
    ReputationRep:
    That's really great help, but how do you know which squares you can use? I don't quite understand the rules for the stepping stone method. Thanks
    Offline

    2
    ReputationRep:
    Try to think about what exactly it is you're doing when you use the stepping stone method.
    You want to add x items to the route with negative index (that's row 3, column 1). In order to keep the total demand on column 1 in check you need to also subtract x from somewhere in column 1. Similarly, you need to subtract x from somewhere in row 3. And then you keep doing this until everything adds up again. And don't add or subtract from any unused cells except the one you started with.

    Have a look at the wiki: http://www.thestudentroom.co.uk/wiki...tion_Algorithm
    • Thread Starter
    Offline

    0
    ReputationRep:
    wow, thank-you so much, that's a great help

Reply

Submit reply

Register

Thanks for posting! You just need to create an account in order to submit the post
  1. this can't be left blank
    that username has been taken, please choose another Forgotten your password?
  2. this can't be left blank
    this email is already registered. Forgotten your password?
  3. this can't be left blank

    6 characters or longer with both numbers and letters is safer

  4. this can't be left empty
    your full birthday is required
  1. Oops, you need to agree to our Ts&Cs to register
  2. Slide to join now Processing…

Updated: September 28, 2007
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

Poll
How do you eat your pizza
Useful resources

Make your revision easier

Maths

Maths Forum posting guidelines

Not sure where to post? Read here first

Equations

How to use LaTex

Writing equations the easy way

Student revising

Study habits of A* students

Top tips from students who have already aced their exams

Study Planner

Create your own Study Planner

Never miss a deadline again

Polling station sign

Thinking about a maths degree?

Chat with other maths applicants

Can you help? Study help unanswered threads

Groups associated with this forum:

View associated groups
Study resources

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22

Registered Office: International House, Queens Road, Brighton, BN1 3XE

Quick reply
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.