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Homework Help: Relative error question

  1. Sep 13, 2009 #1
    1. The problem statement, all variables and given/known data
    A circular disc has a radius of (10 +/- 0.2)cm. Determine the percentage error in the determination of its circumference.

    3. The attempt at a solution
    I know that percentage error is found by absolute error divided by measurement x 100. The absolute error here is 0.2cm, and the measurement is 10cm. But what do I have to do with circumference?
  2. jcsd
  3. Sep 13, 2009 #2
    Have you used the error equation before?

    If we want to work out the absolute error on C and C = 3A, then,

    (error on C)^2 = ((dC/dA)*(error on A))^2

    From memory i think it's that. So imagine the circumference is C and make an equation for it. You should be able to get it from that.
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