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: Finite Math question

  1. Nov 23, 2009 #1
    Add slack variables or subtract surplus variables, and set up the initial simplex tableau:

    Maximize z = 5x1 + 3x2
    subject to:
    2x1 + 5x2 ≤ 50
    x1 + 3x2 ≤ 25
    4x1 + x2 ≤ 18
    x1 + x2 ≤ 12
    with x1≥0, x2 ≥ 0

    Please help.
  2. jcsd
  3. Nov 23, 2009 #2


    User Avatar
    Science Advisor

    Why isn't this in the homework section? And why are you simply stating the problem without showing any work at all? Surely, if you are expected to be able to do a problem like this you must know something about it! What are "slack" variables? How many would you expect this problem to have? What is the "simplex tableau"?

    Are you required to use the simplex tableau? Since there are only two variables, graphing the feasible region is the simplest thing to do.
  4. Nov 23, 2009 #3
    Sorry, I didn't realize that there was a homework help section. And it's not my homework, it's my cousin's. She's been in the hospital for the past week and half so she missed quite a few lectures and is having trouble with her homework. I have a degree in mechanical engineering, so everyone in my family assumes that I know almost everything about math (so not true). Well, I'm fairly certain that I've never done a problem like this before (or I just don't remember doing such problems), so I was looking anywhere for help. I read the chapter, and I got some idea of what the answer should be, but I'm just not sure. The chapter is on other ways to solve these kind of problems besides graphing.

    We think that the answer to the first part is:
    2x_1 + 5x_2 + s_1=50
    x_1+3x_2 + s_2=25
    4x_1+ x_2+s_3=18
    x_1+ x_2 +s_4=12
    x_1≥0, x_2≥0, s_1≥0, s_2≥0, s_3≥0, s_4≥0

    (_1, _2, etc are subscripts)

    And the tableau:
    2 5 1 0 0 0 0 50
    1 3 0 1 0 0 0 25
    4 1 0 0 1 0 0 18
    1 1 0 0 0 1 0 12
    -5 -3 0 0 0 0 1 0

    We're not sure if this is correct since a friend of hers said that she got something different.
  5. Nov 23, 2009 #4


    Staff: Mentor

    It looks like you are on the right track, or close to it. Here's a link to a tutorial that might help you out - http://people.hofstra.edu/Stefan_Waner/RealWorld/tutorialsf4/frames4_3.html [Broken]

    With a degree in ME, you might not have had a class in what is called Linear Programming, which includes solving problems like this one using the Simplex Algorithm.
    Last edited by a moderator: May 4, 2017
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook