Let's solve the volume equation for the radius: start with
[tex]V = \dfrac{4}{3}\pi r^3[/tex]
Multiply both sides by 3:
[tex]3V = 4\pi r^3[/tex]
Divide both sides by 4:
[tex]\dfrac{3V}{4} = \pi r^3[/tex]
Divide both sides by pi:
[tex]\dfrac{3V}{4\pi} = r^3[/tex]
Take the cube root of both sides:
[tex]r = \sqrt[3]{\dfrac{3V}{4\pi}}[/tex]
Now, plug the value for V and you have the radius:
[tex]r = \sqrt[3]{\dfrac{3\cdot 392}{4\pi}} \approx 4.54[/tex]
