Link to PSet
Link to Answer Key.
In this assignment, I've decided to go back to some problems that are more geometric and encourage kids to play with making (and breaking) shapes. You may find that you want either a compass or a small circle stencil for some of these problems...I found a pretty handy stencil for about $2, and they're are fun things to play with that may come up again in future problem sets. If you're really stuck, however, coins of different sizes would probably do the trick.
My main goal in these problems was to give kids an excuse to experiment. To that end you'll find two worksheets worth of "cookies" to chop up in whatever way you like, and I'd definitely say that trying out different kinds of shapes (especially concave vs. convex shapes) is a great way to extend what's going on here.
Finally, if you want to read more about cutting up pastries for the sake of mathematics, Martin Gardner's article about cutting up a real donut is quite funny (especially the reader mail from people who tried to do it and found that real donut-cutting is heavily constrained by the crumbliness of actual donut matter).