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Math Help - How to rearrange to find a variable value

  1. #1
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    How to rearrange to find a variable value

    I have the following:

    log (Ra / Rb) = -0.02 * C * T

    I would like to find Ra = ?

    Kindly help!

    Thanks.
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  2. #2
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    Re: How to rearrange to find a variable value

    Quote Originally Posted by Gunner123 View Post
    I have the following:

    log (Ra / Rb) = -0.02 * C * T

    I would like to find Ra = ?

    Kindly help!

    Thanks.
    Start by exponentiating both sides, making the base whatever the base of the logarithm is...
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  3. #3
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    Re: How to rearrange to find a variable value

    Thanks for your reply...my previous reply disappeared
    There is no base written to log so I assume it is 10.

    would it be :

    10 ^ (Ra / Rb) = 10 ^ (-0.02 * C * T)

    I read an example on wikipedia
    10 ^ 3 = 1000
    log (1000) = 3

    please correct me.

    cheers!
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  4. #4
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    Re: How to rearrange to find a variable value

    Quote Originally Posted by Gunner123 View Post
    Thanks for your reply...my previous reply disappeared
    There is no base written to log so I assume it is 10.

    would it be :

    10 ^ (Ra / Rb) = 10 ^ (-0.02 * C * T)

    I read an example on wikipedia
    10 ^ 3 = 1000
    log (1000) = 3

    please correct me.

    cheers!
    No.

    \displaystyle \begin{align*} \log{\left(\frac{R_a}{R_b}\right)} &= -0.02 \cdot C \cdot T \\ 10^{\log{\left(\frac{R_a}{R_b}\right)}} &= 10^{-0.02 \cdot C \cdot T} \\ \frac{R_a}{R_b} &= 10^{-0.02 \cdot C \cdot T} \end{align*}

    Go from here.
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  5. #5
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    Re: How to rearrange to find a variable value

    ok thanks...I'm going for lunch now will be back

    cheers!
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  6. #6
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    Re: How to rearrange to find a variable value

    Thanks, I also found the alternate working on the basis of:

    Log (a/b) = log a - logb

    Thanks for your prompt help!

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