For this case we have that by definition, the volume of a sphere is given by:

We must find the solution for "r", clearing:
Multiplying by 3 on both sides of the equation:

We divide between
on both sides of the equation:

Finally, we apply cubic root on both sides of the equation:
![r = \sqrt [3] {\frac {3V} {4 \pi}}](https://img.qammunity.org/2020/formulas/mathematics/middle-school/4xjndiv1kkn5o5eb71ztiogbic55qwjn1v.png)
Answer:
![r = \sqrt [3] {\frac {3V} {4 \pi}}](https://img.qammunity.org/2020/formulas/mathematics/middle-school/4xjndiv1kkn5o5eb71ztiogbic55qwjn1v.png)