Results 1 to 5 of 5

Math Help - Word problem.

  1. #1
    Junior Member
    Joined
    Apr 2008
    Posts
    30

    Word problem.

    A rectangular box has dimensions 12 by 16 by 21. Find the length of the diagonal connecting a pair of opposite corners.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor Mathstud28's Avatar
    Joined
    Mar 2008
    From
    Pennsylvania
    Posts
    3,641

    Here is what you should do

    Quote Originally Posted by lilikoipssn View Post
    A rectangular box has dimensions 12 by 16 by 21. Find the length of the diagonal connecting a pair of opposite corners.
    use the Pythagorean theorem in 3-D L=\sqrt{A^2+B^2+C^2}
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member
    Joined
    Apr 2008
    Posts
    30
    Wow thank you! I'd never heard of that.
    Follow Math Help Forum on Facebook and Google+

  4. #4
    o_O
    o_O is offline
    Primero Espada
    o_O's Avatar
    Joined
    Mar 2008
    From
    Canada
    Posts
    1,407
    Drawing a rough sketch of the problem would help a lot. You would find the diagonal, which is in 3-D, can form the hypotenuse of a right triangle with the base being the diagonal of one side of the box and the height simply being the height of the box. Hence, MathStud28's Pythagoras in 3D.

    An illustration found randomly searching (so ignore the numbers):


    Bold blue line can be found by Pythagoras using the bottom side. The 3D diagonal can be found using the bold blue line and the height as mentioned earlier.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Senior Member topher0805's Avatar
    Joined
    Jan 2008
    From
    Vancouver
    Posts
    336
    At your level it is probably best to do it in two steps.

    First, let's assume the base of the box is 12 by 16. Using basic Pythagoras, we know that the diagonal of the base is:

    D=\sqrt {12^2+16^2}

    D=20

    Now, the height of this box must be 21. To find the distance from one corner of the base to the diagonal corner on the top, we simply use the distance formula again:

    D=\sqrt {20^2+21^2}

    D=29
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. word problem - the snow plough problem?
    Posted in the Differential Equations Forum
    Replies: 1
    Last Post: October 13th 2011, 01:02 PM
  2. Replies: 3
    Last Post: January 2nd 2011, 08:20 PM
  3. 1 Word problem and 1 function problem
    Posted in the Algebra Forum
    Replies: 8
    Last Post: April 21st 2010, 08:01 AM
  4. Replies: 2
    Last Post: January 10th 2009, 05:49 AM

Search Tags


/mathhelpforum @mathhelpforum