Results 1 to 3 of 3

Math Help - Really Urgent! derivative problems!

  1. #1
    Newbie
    Joined
    Dec 2008
    Posts
    4

    Really Urgent! derivative problems!

    I really need some help to solve this problem:

    A factory are going to to make cylindershaped cans. The sum of the diameter and height are 80 cm. which measures gives the greatest volume?

    Im sorry for it's a repost but it'll be handed in on a couple of eight hours of beaty sleep. So it would mean the world to me if someone could help me.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    11,863
    Thanks
    639
    d+h = 80

    h = 80 - d

    h = 80 - 2r

    V = \pi r^2 h

    V = \pi r^2(80 - 2r)

    V = 2\pi(40r^2 - r^3)

    find \frac{dV}{dr} and determine the value of r (and hence, the value of d) that maximizes V.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Dec 2008
    Posts
    4
    Well, I get 80r - 3rē

    V'=0

    80r=3rē

    r=80/3

    Is that correct? Or am I way out?
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Need urgent help with some problems!!
    Posted in the Pre-Calculus Forum
    Replies: 5
    Last Post: August 4th 2009, 12:00 AM
  2. Urgent help on 3 problems
    Posted in the Calculus Forum
    Replies: 5
    Last Post: April 29th 2009, 05:37 AM
  3. TI-84 Problems & Questions - Urgent
    Posted in the Calculators Forum
    Replies: 0
    Last Post: March 12th 2009, 06:16 PM
  4. three problems NEED URGENT HELP
    Posted in the Algebra Forum
    Replies: 1
    Last Post: October 22nd 2008, 08:15 PM
  5. URGENT HELP WITH some problems. :x
    Posted in the Pre-Calculus Forum
    Replies: 2
    Last Post: September 2nd 2008, 03:33 PM

Search Tags


/mathhelpforum @mathhelpforum