a GRE Question- Cylinder and Volume

[Roni1985]

1. The problem statement, all variables and given/known data
Jack and Jill each roll a sheet of 9X12 paper to form a cylinder.
Jack tapes the two 9-inch edges together.
Jill tapes the two 12-inch edges together.

Which is greater?
The volume of Jack's Cylinder
or
The volume of Jill's cylinder.

2. Relevant equations

Cylinder Volume: V=pi*r^2*h

3. The attempt at a solution

The problem that I was facing with this question was finding the radii.
However, I looked at the solutions and it says that
Jack's cylinder has a circumference of 12
and Jill's cylinder has a circumference of 9

Jack's height is 9
Jill's height is 12

I don't understand how they derived the circumferences ?!
once I know the circumference I can find the radius.

Thanks.

[Dick]

There's two ways to roll a 9x12 inch piece of paper. If you use the 12 inch side to make the circumference then the 9 inch side must be the height, right? And vice versa? Maybe I don't understand what your question is.

[Roni1985]

There's two ways to roll a 9x12 inch piece of paper. If you use the 12 inch side to make the circumference then the 9 inch side must be the height, right? And vice versa? Maybe I don't understand what your question is.

I'm sorry, my question wasn't clear.
How did they conclude that the circumference is 12 for Jack
and 9 for Jill

[Roni1985]

ohhh, I see it now :\

Thanks.