1. Not finding help here? Sign up for a free 30min 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!

Simple optimization problem

  1. Apr 21, 2008 #1
    [SOLVED] simple optimization problem

    1. The problem statement, all variables and given/known data

    find the dimensions of a rectangle with area 1000 m^2 whose perimeter is as small as possible

    2. Relevant equations

    perimeter = 2x + 2y

    area = xy

    1000 = xy

    y= 1000/x

    perimeter = 2x + 2(1000/x)



    3. The attempt at a solution

    am stuck

    any help from anybody?
     
  2. jcsd
  3. Apr 21, 2008 #2
    perimeter = 2x + 2(1000/x)
    now differentiate!

    should learn concepts from the book (if you don't know why you differentiate)

    Simple approach:

    plot your perimeter and pick and minimum value
    this is realistic problem, so going for really large x and -ve x would be nonsense
     
  4. Apr 21, 2008 #3
    2-(2000/x^2)=0

    i think
     
  5. Apr 21, 2008 #4
    You think? ... have confidence!!!
     
  6. Apr 21, 2008 #5
    2/1000=x^-2
     
  7. Apr 21, 2008 #6

    exk

    User Avatar

    no, try 2=2000/x^2
     
  8. Apr 21, 2008 #7
    x=square root of .001?
     
  9. Apr 21, 2008 #8
    [tex]x=\sqrt{1000}=\sqrt{10\cdot10^2}=10\sqrt{10}[/tex]
     
  10. Apr 21, 2008 #9
    [tex]x=\sqrt{1000}=\sqrt{10\cdot10^2}=10\sqrt{10}[/tex]

    how did u get that?
     
  11. Apr 21, 2008 #10
    [tex]2=\frac{2000}{x^2}\rightarrow x^2=\frac{2000}{2}\rightarrow x^2=1000[/tex]
     
  12. Apr 21, 2008 #11
    thanks alot. am messed up today!
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Simple optimization problem
  1. Optimization Problem (Replies: 3)

  2. Optimization problem (Replies: 10)

Loading...