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Urgent Help Needed in Percentage Error Calculation

  1. Oct 1, 2009 #1
    1. The problem statement, all variables and given/known data

    The quantity Z is a function of 2 variables A and B.
    Z=A^4/B
    A=1.253 (error0.005) B=20.7 (error 0.2)
    Calculate percentage error in Z.


    2. Relevant equations

    I have the relevant error expressions
    if Z=A/B (errorZ/Z)^2 = (errorA/A)^2 + (errorB/B)^2

    if Z=A^n errorZ/Z=n.errorA/A



    3. The attempt at a solution

    I don't know how to combine the different standard error expressions.

    Thanks for any help.
     
  2. jcsd
  3. Oct 1, 2009 #2
    [tex]Z=\frac{A^4}{B}[/tex]

    so in this case

    [tex]\frac{\Delta Z}{Z}=\frac{\Delta \left(A^4\right)}{A^4}+\frac{\Delta B}{B}[/tex]

    and since

    we have

    [tex]\frac{\Delta \left(A^4\right)}{A^4}=4\frac{\Delta A}{A}[/tex]
     
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