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Math Help - Math problem but from Chemistry class..

  1. #1
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    Math problem but from Chemistry class..

    This is actually from my Chemistry class, it's a word problem with basic algebra, so think it belongs in this section.

    Here's the problem:

    The aluminum in a package containing 75ft^2(2 is for square) of kitchen foil weighs approximately 12 ounces. Aluminum has a density of 2.70 g/cm^2. What is the approximate thickness of the aluminum foil in millimeters? (1oz = 28.4 g.)

    I'm getting the answer 0.5521mm. But apparently, that's wrong (according to the book). The solution in the answer key is 1.8 x 10^-2mm.

    Here is what I did:
    I divided the volume by the area; logically, that should give me the thickness:

    340.8g / 2.70g/cm^3 = 126.22

    75ft^2 (100cm^2 / 3.281ft^2)

    126.22cm^3 / 2285cm^2 = 0.055221cm

    0.05521cm x 10mm = 0.5521

    Tell me where I went wrong...
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  2. #2
    Member Mollier's Avatar
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    Hi,

    75ft^2 is 69700cm^2.
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  3. #3
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    Quote Originally Posted by Mollier View Post
    Hi,

    75ft^2 is 69700cm^2.
    I don't follow what you did there.
    According to the book, 100cm equals to 3.281ft.

    How are you getting 69700cm^2 ?
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  4. #4
    Member Mollier's Avatar
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    Hi mate,

    if 100cm = 3.28ft

    then

    100^2cm^2 = 3.28^2ft^2

    (100^2cm^2/3.28^2ft^2)*75ft^2 \approx 69700cm^2.
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