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question about differentiation (rates of change) watch

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    Hi guys,

    I have a query about a 'rates of change' question.

    Basically, the question was to find \frac{dr}{dt}
    From the question, i have obtained the changing rate of volume as \frac{dv}{dt} and \frac{dv}{dr}.



    At first, to find out \frac{dr}{dt}, i used the chain rule connection: \frac{dt}{dv}

. \frac{dv}{dr}. ( i flipped the \frac{dv}{dt} over) But it gave me a wrong answer, i should have flipped \frac{dv}{dr} instead.....

    The question I want to ask is, is it wrong to flip the \frac{dv}{dt} as it has 'dt' as denominator?
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    (Original post by strwbry_short_cake)
    At first, to find out \frac{dr}{dt}, i used the chain rule connection: \frac{dt}{dv}

. \frac{dv}{dr}. ( i flipped the \frac{dv}{dt} over) But it gave me a wrong answer, i should have flipped \frac{dv}{dr} instead.....

    The question I want to ask is, is it wrong to flip the \frac{dv}{dt} as it has 'dt' as denominator?
    The method you used would give \frac{dt}{dr}
    \frac{dt}{dv} . \frac{dv}{dr} = \frac{dt}{dr}

    It doesn't really matter which of the differentials you flip over, but using your method, to get \frac{dr}{dt} you have to do \frac{dr}{dt}=\frac{1}{\frac{dt}  {dr}}
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    ah yes of course it would...=S
    thanks so much!
 
 
 
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