Results 1 to 11 of 11

Math Help - help!! polynomial

  1. #1
    Junior Member
    Joined
    Sep 2008
    Posts
    56

    help!! polynomial

    heres a question i dunt get how to solve, the width of a square based storage 3m less than its height. THe tank has a capacity of 20m^3. If the deimension are integer value in metres, what are they?
    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
    width of a square based storage 3m less than its height. THe tank has a capacity of 20m^3.
    w = h-3

    area of base, B = (h-3)^2

    V = Bh = h(h-3)^2 = 20

    h^3 - 6h^2 + 9h - 20 = 0

    rational root theorem ... possible positive integer roots {1, 2, 4, 5, 10, 20}

    go for it.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by lickman View Post
    heres a question i dunt get how to solve, the width of a square based storage 3m less than its height. THe tank has a capacity of 20m^3. If the deimension are integer value in metres, what are they?
    V = h(h-3)^2. But V = 20. Therefore 20 = h(h-3)^2. Solve for h.

    Trial and error is an efficient way of getting h and therefore getting the dimensions of the tank.
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor
    Joined
    Oct 2005
    From
    Earth
    Posts
    1,599
    Quote Originally Posted by lickman View Post
    heres a question i dunt get how to solve, the width of a square based storage 3m less than its height. THe tank has a capacity of 20m^3. If the deimension are integer value in metres, what are they?

    So the volume of this container is W*W*H. We know that W=H-3, so let's plug that in. The volume is 20m^3, so (H-3)(H-3)H=20.

    Can you solve it from here?

    EDIT: I am WAY late.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Junior Member
    Joined
    Sep 2008
    Posts
    56
    volume is W*W*H? why is W*W? isnt W x L x H lol i'm seriously retarded so plz forgive me/
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Flow Master
    mr fantastic's Avatar
    Joined
    Dec 2007
    From
    Zeitgeist
    Posts
    16,948
    Thanks
    5
    Quote Originally Posted by lickman View Post
    volume is W*W*H? why is W*W? isnt W x L x H lol i'm seriously retarded so plz forgive me/
    The base is a square , is it not?
    Follow Math Help Forum on Facebook and Google+

  7. #7
    Junior Member
    Joined
    Sep 2008
    Posts
    56
    lmfao thanks , but i seriously dunt know these anymore, base always b^2[/tex]? anyway i need some knowledge in geometry or shape calculating before solving these. lol
    Follow Math Help Forum on Facebook and Google+

  8. #8
    Junior Member
    Joined
    Sep 2008
    Posts
    56
    is there anyway for a easier to analysis problem solving question with factors etc
    Follow Math Help Forum on Facebook and Google+

  9. #9
    MHF Contributor
    Joined
    Oct 2005
    From
    Earth
    Posts
    1,599
    Quote Originally Posted by lickman View Post
    is there anyway for a easier to analysis problem solving question with factors etc
    I don't understand this sentence. Can you please explain?
    Follow Math Help Forum on Facebook and Google+

  10. #10
    Junior Member
    Joined
    Sep 2008
    Posts
    56
    is there anyway for a easier to analysis problem solving question with factors etc
    lol sorry for my jibberish english
    is there anyway to make it easier to analysis problem solving questions with factors? by certain words they use etc..
    Follow Math Help Forum on Facebook and Google+

  11. #11
    MHF Contributor
    Joined
    Oct 2005
    From
    Earth
    Posts
    1,599
    Quote Originally Posted by lickman View Post
    is there anyway for a easier to analysis problem solving question with factors etc
    lol sorry for my jibberish english
    is there anyway to make it easier to analysis problem solving questions with factors? by certain words they use etc..
    Hmm, good question. I don't know if I can answer that in general, but I'll tell you the key words for this problem.

    "square base" - this means that the length and width are equal.
    "width... 3m less than its height" - this is great because we can now relate the width to the height.
    "capacity of 20m^3" - we got the volume of the container now.

    Now I think how do I put this together and use it. Well the volume of a box is the L*W*H, length times width times height. We know this equals 20. So the length and width of the base are the same as we said before, so we can say W*W*H=20. Now the width is 3 meters less than the height. Write that out just like it sounds. W = H-3. Now you can substitute this in and you got your answer.

    I don't know if that helps at all, but my advice is look for all the key info given. Write down the numbers given and what they pertain to. The hardest part usually will be making some kind of substitution, so look for some kind of relation that you can use to make a substitution.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 1
    Last Post: October 23rd 2011, 06:36 AM
  2. Replies: 1
    Last Post: February 24th 2011, 06:46 PM
  3. Replies: 1
    Last Post: December 15th 2009, 07:26 AM
  4. [SOLVED] dividing polynomial by a polynomial
    Posted in the Algebra Forum
    Replies: 1
    Last Post: February 3rd 2008, 02:00 PM
  5. dividing a polynomial by a polynomial
    Posted in the Algebra Forum
    Replies: 1
    Last Post: August 2nd 2005, 12:26 AM

Search Tags


/mathhelpforum @mathhelpforum