#1**+2 **

What information are you given?

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

hectictar May 11, 2017

#3**+3 **

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 r^{2} Replace " surface area " with " 13r ".

13r = 4π r^{2} 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

hectictar May 12, 2017