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# What is the equation for finding the volume and radius of a sphere

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What is the equation for finding the d radius of a sphere

May 11, 2017

#1
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What information are you given?

Do you know the volume, the surface area, the circumference, or maybe the diameter?

May 11, 2017
#2
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I mean the radius and volume

Surface area is 13r

May 11, 2017
edited by Guest  May 12, 2017
#3
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Oh okay...Assuming that the " r " in " 13r " stands for the radius......

The formula for the surface area of a sphere is:

surface area = 4π r2          Replace " surface area " with " 13r ".

13r = 4π r2                         Divide both sides of the equation by r.

13 = 4π r                            Divide both sides of the equation by 4π.

13/(4π) = r

So, the radius =  $$\frac{13}{4\pi}$$   units

The formula for the volume of a sphere is:

volume = $$\frac43 \pi r^3$$                 Replace " r " with " $$\frac{13}{4\pi}$$ ".

volume = $$\frac43 \pi (\frac{13}{4\pi})^3$$           Simplify.

volume = $$\frac43\pi(\frac{2197}{64\pi^3}) = \frac43(\frac{2197}{64\pi^2}) = \frac{2197}{48\pi^2}$$     cubic units

May 12, 2017