Posted by Johnny on Wednesday, September 1, 2010 at 10:17am.
I need help on two problems :P
1. A spherical balloon is partially blown up and its surface area is measured. More air is added increasing the volume of the balloon. If the surface area of the balloon expands by a factor of 2.0 during this procedure, by what factor does the radius of the balloon change?
2. A poster advertising a student election candidate is too large according to the election rules. The candidate is told she must reduce the length and width of the poster by 20.0%. By what percentage will the area of the poster be reduced?

Physics  drwls, Wednesday, September 1, 2010 at 11:04am
1. Area is proportional ot the square of radius. Therefore, to double the area, muliply the radius by sqrt2 = 1.414
2. (0.8)^2 = 0.64 is (new area)/(old area)
The reduction percent is 10.64 = 36%
This is really not physics.