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Math Help - Density

  1. #1
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    Density

    this is my question:

    calculate the volume of a piece of wood which weighs 102g and has a density of 0.85g/cm^3?

    would i do 0.85 x 102 =86.7 cm^3?
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  2. #2
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    Think about your units. They will save you.

    By multiplying the two given values, your units are \frac{gm^{2}}{cm^{3}}. Does that look like volume to you?

    If you divide the mass by the density, you get \frac{gm}{\frac{gm}{cm^3}}\;=\;cm^{3}. Does that look like volume?

    Additionally, you should seek clarity from the definitions. What is the definition of density? Find it in your book. Mass/Volume? Something like that? Well, if you have Density = Mass/Volume and you are given Mass and Density, you are left with only a small algebra problem. Substitute and solve.

    Note: Make sure you know the difference between Weight and Mass. They are NOT the same thing.
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  3. #3
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    would it be 1.25/4?
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  4. #4
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    Are you just making stuff up? Try using the values you were given.

    Also, where are the units? Keep the units. Use the units. BE the units. They WILL save you.
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  5. #5
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    0.85/102= 0.0083 cm^3
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  6. #6
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    Quote Originally Posted by andyboy179 View Post
    calculate the volume of a piece of wood which weighs 102g and has a density of 0.85g/cm^3?
    If you had included the units, rather than just guessing, you would have done this:

    (0.85 g/cm^3)/(102 g) = (0.85/102)*(1/cm^3)

    Is 1/cm^3 volume? No! cm^3 would be volume.

    (102 g) / (0.85 g/cm^3) = ??
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