how can I find radius of a cylinder with surface area and height

[KATheBurger]

How can I find the radius of a cylinder if I only know the surface area and the height?
The surface area is 200 cm and the height is 86 cm.

 

[Deleted member 4993]

How can I find the radius of a cylinder if I only know the surface area and the height?
The surface area is 200 cm and the height is 86 cm.

What is the formula for surface area of a cylinder? It should be in your text-book/class-notes!

Please show us what you have tried and exactly where you are stuck.

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[skeeter]

assuming total surface area is given ...

[MATH]A = 2\pi r^2 + 2\pi rh \implies 2\pi r^2 + 2\pi h r - A = 0[/MATH]
[MATH]r = \dfrac{-2\pi h + \sqrt{(2\pi h)^2 + 8A \pi}}{4\pi}[/MATH]
if it's lateral surface area that is given ...

[MATH]A = 2\pi r h \implies r = \dfrac{A}{2\pi h}[/MATH]
... oh, and area is [MATH]200 \, cm^2[/MATH]