Each week, we post a new Challenge Problem for you to attempt. If you submit the correct answer, you will be entered into that week’s drawing for two free Manhattan Prep GRE Strategy Guides.

In the figure above, an unshaded circle with diameter x is surrounded by a shaded region with uniform width of 2.  For what values of x is the area of the unshaded circle greater than the area of the shaded region?

See the answer choices and submit your pick over on our Challenge Problem page.