Answer: 2.524 ft
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The equation for the surface area of a sphere is [tex]SA = 4 \pi r^2[/tex].
SA = surface area
r = radius
You're told that the surface area, SA = 80 square feet. Plug that into the equation and solve for r:
[tex]80 = 4 \pi r^2\\
20 = (3.14) r^2\\
r^2 = \frac{20}{3.14} \\
r = \sqrt{ \frac{20}{3.14}}\\
r \approx 2.524 \: ft[/tex]
