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Homework Help: Uncertainty for a ratio ( help!)

  1. Aug 26, 2010 #1
    Uncertainty for a ratio (urgent help!)

    Question: As you eat your way through a bag of chocolate chip cookies, you observe that each cookie is a circular disk with a diameter of d = 8.32 cm +/-1×10−2 cm and a thickness of h = 9.3×10−2 cm +/-1×10−3 cm.
    Find the uncertainty in this ratio of the diameter to the thickness.

    Hint:Notice the division.
    If we are dividing that is a negative exponent.

    The ratio of the diameter to the thickness is 89.5. How can I use the calculus error prop./the partial derivative to solve this? The hint also made things more confusing.
    Someone said to said it up like this or something: d*h^-1, but I still don't understand.
    Plus, I don't see how you can get a ratio from the partial derivative formula. And I tried manipulating the volume formula: v=[(pi d^2)/4]*h, but it can't go to d/h....

    I was spending my time yesterday and today just to solve this problem and I couldn't figure it out and it was the only problem I had trouble with....sorry I'm very frusterated right now >:[
    Last edited: Aug 26, 2010
  2. jcsd
  3. Aug 26, 2010 #2
    Re: Uncertainty for a ratio (urgent help!)

    nevermind I figured it out :)
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