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# Rearanging nightmare. Watch

1. 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

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! :-?
2. isnt the surface area:

?
3. (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

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

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 Not And how have you let ?
4. Talk about number blind. Thank you so much. I know now why I was getting nowhere; stupid little mistakes! Thanks again.

Updated: May 5, 2012
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