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Math Help - [SOLVED] Need help understanding this question.

  1. #1
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    [SOLVED] Need help understanding this question.

     <br />
\frac {\sigma_z}{z} = \frac {\sigma_x}{x} + \frac {\sigma_y}{y}<br />

    For z=x+y
    where x=30cm +/- 5cm
    and y=40cm +/- 8cm

    I don't understand what to do here, I guess I don't know what they are asking. How does this get set up?

    How do I do the z, x, and y parts? Do I need to do it 2x, once for + and another for -?
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  2. #2
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    Quote Originally Posted by redman223 View Post
     <br />
\frac {\sigma_z}{z} = \frac {\sigma_x}{x} + \frac {\sigma_y}{y}<br />

    For z=x+y
    where x=30cm +/- 5cm
    and y=40cm +/- 8cm

    I don't understand what to do here, I guess I don't know what they are asking. How does this get set up?

    How do I do the z, x, and y parts? Do I need to do it 2x, once for + and another for -?
    Substitute x = 30, \sigma_x = 5, y = 40, \sigma_y = 8, z = x + y = 70.

    Solve for \sigma_z.

    It's expected you've got some familiarity with error analysis.
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