The volume of the sphere by definition is:

Clearing the radio we have:
![r = \sqrt[3]{ (3V)/(4 \pi)}](https://img.qammunity.org/2019/formulas/mathematics/high-school/j62mte1dginfah73m5zmuvn5pgb2hw14qu.png)
For the initial condition we have that the radius is:

For the final condition we have that the radius is:

Then, the difference between both values is given by:
Answer:
the radius increase 0.62 inches when the volleyball is fully inflated