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Rearanging nightmare.

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    I can't for the life of me rearrange the following equation. It is part of a differentiation question where I need to create a formula for volume, V. The question is as follows;

    A closed cylinder has a total surface area of 600 pi. show that the volume of this cylinder is given by the formula V= 300πr - πr^3

    r= radius of cylinder

    I know that;
    A = 2πrh(2πr^2)
    V = πr^2h
    therefore
    600π = 2πrh(2πr^2) - I need to rearrange this on the left to make h the subject so i can plug it into the volume formula to give me V= 300πr - πr^3.

    I've tried a thousand ways but can't seem to get it, please help before I crack! :-?
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    isnt the surface area:

     2 \pi rh + 2 \pi r^2 ?
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    (Original post by monkfishkev)
    I can't for the life of me rearrange the following equation. It is part of a differentiation question where I need to create a formula for volume, V. The question is as follows;

    A closed cylinder has a total surface area of 600 pi. show that the volume of this cylinder is given by the formula V= 300πr - πr^3

    r= radius of cylinder

    I know that;
    A = 2πrh(2πr^2)
    V = πr^2h
    therefore
    600π = 2πrh(2πr^2) - I need to rearrange this on the left to make h the subject so i can plug it into the volume formula to give me V= 300πr - πr^3.

    I've tried a thousand ways but can't seem to get it, please help before I crack! :-?

    (Original post by monkfishkev)
    I can't for the life of me rearrange the following equation. It is part of a differentiation question where I need to create a formula for volume, V. The question is as follows;

    A closed cylinder has a total surface area of 600 pi. show that the volume of this cylinder is given by the formula V= 300πr - πr^3

    r= radius of cylinder

    I know that;
    A = 2πrh(2πr^2)
    V = πr^2h
    therefore
    600π = 2πrh(2πr^2) - I need to rearrange this on the left to make h the subject so i can plug it into the volume formula to give me V= 300πr - πr^3.

    I've tried a thousand ways but can't seem to get it, please help before I crack! :-?
    Surface Area  \displaystyle = 2\pi r^2 + 2\pi rh Not  \displaystyle 2\pi rh And how have you let  \displaystyle h = r ?
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    Talk about number blind. Thank you so much. I know now why I was getting nowhere; stupid little mistakes! Thanks again.

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Updated: May 5, 2012
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