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Math Help - log and natural log

  1. #1
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    log and natural log

    i have no idea if im doing this correct

    400 = (1 - e^-.2t
    ln400 = -.2tln(500(1- e)
    .2t = ln(500(1 - e)
    ln(400)

    im stuck here, any help would be great

    im trying to solve for T which indicates times in the problem
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  2. #2
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    Quote Originally Posted by jasimmons86 View Post
    i have no idea if im doing this correct

    400 = (1 - e^-.2t
    ln400 = -.2tln(500(1- e)
    .2t = ln(500(1 - e)
    ln(400)

    im stuck here, any help would be great

    im trying to solve for T which indicates times in the problem

    Is this your problem?

     400 = 1-e^{.2t}
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  3. #3
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    there shpould be a negative(-) before the .2

    but otherwise yes
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  4. #4
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    no, typed the equation wrong

    here is the correct one

    400 = 500(1-e^ -.2t)

    solve for t
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  5. #5
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    1 - e^{-.2t} = \frac{400}{500}

    1 = \frac{400}{500} + e^{-.2t}

    1 = \frac{4}{5} + e^{-.2t}

    1 - \frac{4}{5} = e^{-.2t}

    \frac{1}{5} = e^{-.2t}

    0.2 = e^{-.2t}
    Last edited by icemanfan; February 13th 2010 at 12:12 PM. Reason: changed equation
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