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Thread: (1 of 2) Rearrange equation to make R the subject.

  1. #1
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    Question (1 of 2) Rearrange equation to make R the subject.

    Hi guys,

    Can anybody point me in the right direction to solve this equation? Iím trying to develop my math skills in preparation for an OU degree this Autumn. But my mind has just gone blank and canít understand how to solve it

    The question:
    Rearrange the following expression to make R the subject, where R > 0

    h = R^2 / L + L

    I have lots more of these practise questions to get through, so this is just to help me figure out how to solve it correctly

    also, I should mention that I have another question which Iíve made a separate post about as itís not directly related to the problem in this thread (hence 1 of 2 in title)

    Thanks guys!
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  2. #2
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    Re: (1 of 2) Rearrange equation to make R the subject.

    Here's the general idea. If you were given a value for "R" and asked to evaluate "h" you would
    1) square h-- That's R^2
    2) divide by L-- That's R^2/L
    3) add L-- That's R^2/L+ L which is equal to h.

    Here the problem is the opposite, you want to solve for R. So do the opposite! Do the opposite of each step above, in the opposite order:
    1) subtract L-- That gives R^2/L+ L- L= R^2/L. And since you must "do the same thing to both sides", R^2/L= h- L.

    2) multiply by L-- That gives R^2. And since you must "do the same thing to both sides", R^2= L(h- L)= Lh- L^2.

    3) Take the square root-- That gives R. And since you must "do the same thing to both sides", R= sqrt(Lh- L).
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  3. #3
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    Re: (1 of 2) Rearrange equation to make R the subject.

    Ah! I get it! Thank you!!!

    Sorry this isn’t strictly related. But do you recommend any sources to help improve my math? Looking at these questions it’s actually rather embarrassing how little I know.

    Thanks!
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  4. #4
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    Re: (1 of 2) Rearrange equation to make R the subject.

    Quote Originally Posted by HallsofIvy View Post
    3) Take the square root-- That gives R.
    And since you must "do the same thing to both sides", R= sqrt(Lh- L).
    R = sqrt(Lh - L^2) ; typo?
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  5. #5
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    Re: (1 of 2) Rearrange equation to make R the subject.

    Yes, thanks for the correction.
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    Re: (1 of 2) Rearrange equation to make R the subject.

    Quote Originally Posted by Anticlimactic View Post
    Ah! I get it! Thank you!!!

    Sorry this isn’t strictly related. But do you recommend any sources to help improve my math? Looking at these questions it’s actually rather embarrassing how little I know.

    Thanks!
    It depends on what you want to do with math. If you want to make sure you understand the basics, and that is enough for you, I would recommend anything in the "For Dummies" series (such as Basic Math For Dummies). While the title of the book sounds a bit patronizing, they tend to be fairly well laid-out, making learning from them relatively straightforward.

    On the other hand, if you are looking for a deeper understanding, I would recommend taking classes. While self-study can take you far, it is difficult to hone in on important details without a mentor guiding you. That is not to say it is not possible, but certainly more difficult.
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