The equation for the volume of a sphere is as follows:
[tex]V= \frac{4}{3}(pi)r^{3} [/tex]
Using this, you can plug in the radius, 6.5 ft. and get the equation you need:
[tex]V= \frac{4}{3}(pi)6.5^{3} [/tex]
Then, you cube 6.5:
(6.5)(6.5)(6.5)= 274.625
Then, you just multiply [tex] \frac{4}{3} [/tex] by π and 274.625
Your final answer is:
V ≈ 1,150 [tex] ft^{2} [/tex]
