Results 1 to 7 of 7

Math Help - What is the value of the dimensions?

  1. #1
    rcs
    rcs is offline
    Senior Member rcs's Avatar
    Joined
    Jul 2010
    From
    iligan city. Philippines
    Posts
    455
    Thanks
    2

    What is the value of the dimensions?

    [B]Problem:
    A farm has a perimeter of 55 km and has an area of 150 km sq. Find the dimensions of the farm.

    i tried to answer on this that
    A= l x w P = 2 (l + w)
    150 km sq. = l x w 55 km = 2 (l +w)

    what is next to here? do i need to manipulate the formula? i'm stuck here.
    Please does anybody can help me on this?
    Thank you
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    11,621
    Thanks
    426
    Quote Originally Posted by rcs View Post
    [B]Problem:
    A farm has a perimeter of 55 km and has an area of 150 km sq. Find the dimensions of the farm.

    i tried to answer on this that
    A= l x w P = 2 (l + w)
    150 km sq. = l x w 55 km = 2 (l +w)

    what is next to here? do i need to manipulate the formula? i'm stuck here.
    Please does anybody can help me on this?
    Thank you
    LW = 150<br />

    L = \dfrac{150}{W}

    2(L+W) = 55

    2\left(\dfrac{150}{W} + W\right) = 55

    solve for W , then determine L
    Follow Math Help Forum on Facebook and Google+

  3. #3
    rcs
    rcs is offline
    Senior Member rcs's Avatar
    Joined
    Jul 2010
    From
    iligan city. Philippines
    Posts
    455
    Thanks
    2
    thanks a lot
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor

    Joined
    Apr 2005
    Posts
    14,973
    Thanks
    1121
    Or, the other way: 2(L+ W)= 55 so L+ W= 55/2 and then W= 55/2- L. LW= L(55/2- L)= (55/2)L- L^2= 150.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    rcs
    rcs is offline
    Senior Member rcs's Avatar
    Joined
    Jul 2010
    From
    iligan city. Philippines
    Posts
    455
    Thanks
    2

    answer

    2(150/w + w) = 55
    2(150+w^2w) = 55
    (300+ 2w^2) / w = 55
    300+ 2w^2 = 55w
    2w^2 - 55w + 300 = 0
    (2w - 15 ) ( w - 20) = 0
    w = 20 or w = 15/2 or 7.5

    LW = 150 if w = 20
    L = 150/20
    L = 7.5

    LW = 150 if w = 7.5
    L = 150/7.5
    L = 20


    which of this two values is right/ correct for the L ?
    Follow Math Help Forum on Facebook and Google+

  6. #6
    rcs
    rcs is offline
    Senior Member rcs's Avatar
    Joined
    Jul 2010
    From
    iligan city. Philippines
    Posts
    455
    Thanks
    2

    answer

    2(150/w + w) = 55
    2(150+w^2/w) = 55
    (300+ 2w^2) / w = 55
    300+ 2w^2 = 55w
    2w^2 - 55w + 300 = 0
    (2w - 15 ) ( w - 20) = 0
    w = 20 or w = 15/2 or 7.5

    LW = 150 if w = 20
    L = 150/20
    L = 7.5

    LW = 150 if w = 7.5
    L = 150/7.5
    L = 20


    which of this two values is right/ correct for the L ?
    Follow Math Help Forum on Facebook and Google+

  7. #7
    MHF Contributor

    Joined
    Apr 2005
    Posts
    14,973
    Thanks
    1121
    They are both correct. Both say that one side has a length of 7.5 km and the other 20 km. You have only switched which side you call "length" and which you call "width".
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. box dimensions
    Posted in the Calculus Forum
    Replies: 5
    Last Post: December 20th 2009, 03:22 PM
  2. dimensions
    Posted in the Algebra Forum
    Replies: 5
    Last Post: April 7th 2009, 08:45 AM
  3. Box Dimensions
    Posted in the Algebra Forum
    Replies: 3
    Last Post: March 9th 2009, 08:12 AM
  4. Dimensions
    Posted in the Advanced Applied Math Forum
    Replies: 1
    Last Post: October 3rd 2008, 09:24 AM
  5. Dimensions of a pen????
    Posted in the Calculus Forum
    Replies: 3
    Last Post: October 21st 2007, 12:34 PM

Search Tags


/mathhelpforum @mathhelpforum