Results 1 to 2 of 2

Math Help - Help with word problems please

  1. #1
    Newbie
    Joined
    Nov 2009
    Posts
    8

    Help with word problems please

    A can is to be constructed in the form of a right circular cylinder. If it is to contain 128 pi cm^3, what dimensions will require the least amount of material.

    This is what I did:

    pir^2h = 128pi
    solved for h
    h = 128/r^2
    since
    2pirh + 2pir^2 = surface area
    so
    256pi/r + 2pir^2
    graphed it to find the min., but what I got requires r = 0, which can't be right?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    11,690
    Thanks
    448
    Quote Originally Posted by ggeek101 View Post
    A can is to be constructed in the form of a right circular cylinder. If it is to contain 128 pi cm^3, what dimensions will require the least amount of material.

    This is what I did:

    pir^2h = 128pi
    solved for h
    h = 128/r^2
    since
    2pirh + 2pir^2 = surface area
    so
    256pi/r + 2pir^2
    graphed it to find the min., but what I got requires r = 0, which can't be right?
    redo your graph ... mine shows the minimum to be close to r = 4
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. word problems >_<
    Posted in the Algebra Forum
    Replies: 1
    Last Post: December 14th 2011, 07:35 PM
  2. Problems with integration word problems
    Posted in the Calculus Forum
    Replies: 5
    Last Post: April 25th 2010, 05:39 PM
  3. Word Problems
    Posted in the Pre-Calculus Forum
    Replies: 3
    Last Post: November 6th 2009, 12:01 PM
  4. Max/min word problems!
    Posted in the Calculus Forum
    Replies: 1
    Last Post: March 26th 2009, 06:54 AM
  5. how do u do these word problems?
    Posted in the Pre-Calculus Forum
    Replies: 6
    Last Post: March 29th 2008, 02:54 PM

Search Tags


/mathhelpforum @mathhelpforum