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Thread: question about related rates problem

  1. #1

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    question about related rates problem

    In doing these related rates words problem, there is one small step I don't understand....wondered if someone could tell me how it is being done.

    How do you go from

    dV/dt = [(pi/4) * (h^2)] * dh/dt

    to

    dh/dt = [4 / (pi * h^2)] * dV/dt

    So basically, I'm not sure how they are going from (pi/4) h^2 to 4/(pi h^2)

    In another problem I am doing, I want to get dV/dt by itself from this equation:

    dS/dt = 12s dV/dt

    and I'm not sure how the 12s part would be changed as a result of pulling the dV/dt to the other side

  2. #2
    Frenzied Member zaza's Avatar
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    Re: question about related rates problem

    Hi,

    Maybe I have misunderstood the question. Are you really telling me you're doing differential equations and can't rearrange either of those two?

    Part 1) They are the same thing!!! You multiply both sides by 4 and divide both sides by Pi * (h^2) !!!!!

    Part 2) You divide both sides by 12s!!!!!!!!!!!!!

    I don't think it can actually be said any simpler than this. If you still don't understand then I think an entire course in basic algebra is what you need - there are a fair few math help sites about which can get you started on this front.
    If I have misunderstood, then feel free to enlighten me...

    zaza

  3. #3
    vbuggy krtxmrtz's Avatar
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    Re: question about related rates problem

    Quote Originally Posted by zaza
    Hi,

    Maybe I have misunderstood the question. Are you really telling me you're doing differential equations and can't rearrange either of those two?
    zaza
    Darth Predator, it sounds like you have to write a book in Russian and don't even know the Cyrillic alphabet!
    We can certailnly help you with loose questions, but as zaza rightly points out you badly need a basic course.
    Lottery is a tax on people who are bad at maths
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