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Math Help - Minimizing Surface Area

  1. #1
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    Minimizing Surface Area

    United Parcel Service has contracted you to design a closed box with a square base that has a volume of 5000 cubic inches.

    Find a function for the surface area of the box.

    NOTE: There is a diagram of a box having length = x, width = x and height = y
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  2. #2
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    Quote Originally Posted by fdrhs View Post
    United Parcel Service has contracted you to design a closed box with a square base that has a volume of 5000 cubic inches.

    Find a function for the surface area of the box.

    NOTE: There is a diagram of a box having length = x, width = x and height = y
    The area of the base and top are both x^2, the area of each of the four
    sides is xy. There for the totl surface area is:

    A=2x^2+4xy square inches (assume x and y are in inches).

    We are also told that the volume of the box is 5000 cubic inches, but we also
    know that the volume of the box is length times breadth times height=x^2y.

    so: x^2y=5000, or y=5000/x^2. So now substitute this back into the
    equation for the surface area:

    A=2x^2+4x(5000/x^2)=2x^2+20000/x square inches.

    RonL
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  3. #3
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    fdrhs

    You said:

    "...the volume of the box is length times breadth times height."

    What does the word BREADTH mean?

    I thought the volume is: V = (length) (width) (height)?

    Does width = breadth?
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  4. #4
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    hey

    How was I to know this is a calculus question?

    The question is found in my pre-calculus textbook.

    Why would I post the question in the pre-calculus section?
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  5. #5
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    Quote Originally Posted by fdrhs View Post
    You said:

    "...the volume of the box is length times breadth times height."

    What does the word BREADTH mean?

    I thought the volume is: V = (length) (width) (height)?

    Does width = breadth?
    yes, width=breadth.
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  6. #6
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    Quote Originally Posted by fdrhs View Post
    How was I to know this is a calculus question?

    The question is found in my pre-calculus textbook.

    Why would I post the question in the pre-calculus section?
    What are you refering to?

    This is definitely a pre-calculus question as asked here, it does not ask you to maximise or find a rate of change of anything, does it? (except in the title)


    RonL
    Last edited by CaptainBlack; January 31st 2007 at 10:29 PM.
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  7. #7
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    ok

    I was given an infraction and threatened here on this site for placing this question in the precalculus section. Is that a crime?

    People get kicked out of this site easily, don't they?

    I am a newbie and have already been threatened by the tutors here.

    Is this wise?

    This site will loose its students if this continues.
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  8. #8
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    Quote Originally Posted by fdrhs View Post
    I was given an infraction and threatened here on this site for placing this question in the precalculus section. Is that a crime?

    People get kicked out of this site easily, don't they?

    I am a newbie and have already been threatened by the tutors here.

    Is this wise?

    This site will loose its students if this continues.
    Obviously this was from ThePerfectHacker.
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  9. #9
    Grand Panjandrum
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    Quote Originally Posted by fdrhs View Post
    It does not matter who the e-mail came from.

    What did I do to deserve an infraction as a new guy here?

    It is a BIG CRIME to post questions in the wrong place BY MISTAKE?????
    An infraction is not a big deal here, just lets you know that its not
    acceptable to make a habit of whatever its given for.

    Also remember that the moderators can become somewhat less tolerant
    on days where they have to spend considerable time tidying up rather than
    doing something more interesting.

    I forget the exact numbers, but you need multiple infractions within a few
    days of one another to qualify for a short ban.

    RonL
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