"Charged Balloon Expands When Blown Up

[tuggler]

Homework Statement

The charged balloon expands as it is blown up, increasing in size.

Here is a link. It is question 15.

http://cf.linnbenton.edu/mathsci/physci/rajabza/upload/wkbk_solutions_27.pdf

Homework Equations

The Attempt at a Solution

Is that answer correct? Because what I was thinking was since the balloon surface area was increasing then the density decreases hence all the points are decreasing? Am I wrong and the answer provided in the link correct?

 

[mfb]

The answer there is correct.
The density is decreasing, but the surface area is increasing.

 

[tuggler]

Thank you!