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  1. #1
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    conversions

    As you might know, there are now businesses asking you to send in your old jewelry in exchange for cash. Imagine you have a solid gold sphere of 15.7 mm diameter which you decide to send in for cash. If the company offers $125 per ounce of gold, how much money will they send you given that the density of gold is 19.31 g/cm^3.

    1 ounce = 28.3495231 grams
    1 cm^3 = 1000mm^3

    19.31g/cm^3 x 1 ounce/28.3495231 g x cm^3/1000mm^3 =

    = 4.8275 ounces/mm^3

    (15.7mm)^3 = 3,869.893mm^3 x 4.8275 ounces/mm^3 = 18,681.90846 ounces x $ 125 = 2,335, 238.557 dollars...which leads me to believe this is wrong.
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  2. #2
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    V = \frac{4}{3}\pi \left(\frac{1.57}{2}\right)^3 = 2.026... cm^3

    M = \rho V = 19.31 \cdot 2.026... = 39.1273... g

    \frac{39.1273...}{28.3495...} \cdot 125 = 172.52 dollars


    must be a very old problem ... gold is going for much more than $125 per ounce these days.
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  3. #3
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    I don't get the 1.57/2 part.
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  4. #4
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    Quote Originally Posted by A Beautiful Mind View Post
    I don't get the 1.57/2 part.
    15.7 mm = 1.57 cm = the diameter.

    So the radius = 1.57/2 cm.
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