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 survey to be in with the chance of winning a £50 Amazon voucher or one of 5 x £10 Amazon vouchers 24-05-2016
  1. Offline

    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
  2. File Type: bmp d2pic1.bmp (414.0 KB, 141 views)
  3. Offline

    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.
  4. Offline

    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
  5. Offline

    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
  6. Offline

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


Submit reply


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.

Today on TSR

OCR Physics Breadth exam

Chat about the exam here

Are you registered to vote in the EU referendum?
Useful resources

Make your revision easier


Maths Forum posting guidelines

Not sure where to post? Read here first


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