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Thread: [SOLVED] natural log

  1. March 9th 2009, 11:34 AM #1
    brentwoodbc
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    [SOLVED] natural log

    P=130e^{-.000155h}
    find h when P = 8.5

    8.5=130e^{-.000155h}

    answer is 17600

    I take LN of both sides then solve for h but I get -2353?
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  2. March 9th 2009, 11:38 AM #2
    e^(i*pi)
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    Quote Originally Posted by brentwoodbc View Post
    P=130e^{-.000155h}
    find h when P = 8.5

    8.5=130e^{-.000155h}

    answer is 17600

    I take LN of both sides then solve for h but I get -2353?
    What steps did you do? Mine are below to check against



    e^{-0.000155h} = 8.5/130

    take natural logs:

    -0.000155h = ln{(\frac{8.5}{130})}

    h = \frac{1}{-0.000155}\cdot ln{(\frac{8.5}{130})} = 17600 (3sf)
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  3. March 9th 2009, 11:47 AM #3
    brentwoodbc
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    Lightbulb

    k I got It, I was typing it into my calculator wrong, thanks again
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