I often have the most difficult questions last in independent practice. Question #7 is one of those problems. I think that perhaps it should go to the front so that students have to deal with the most difficult problems first. The reason it is last is because the preceding problems are designed to make sure a student can use the surface area formula with ease.
Part a of question 7 did not pose much difficulty. Afterall, it just requires finding the volume of the brie - it's in the form of a cylinder.
Part b is another story all together. Many of my students were not able to visualize how the cheese looked after the wedge was removed. It would have been nice to have a model. Perhaps a Reese's Peanut Butter Cup could have filled the role. We had to draw it to see that to rectangular surfaces that are 3 in by 1 in become exposed.
I had a line of questions to help students work through the problem:
1) How much of the total surface area is removed with the wedge? [one-eighth]
2) What shapes appear after the wedge is removed? [two rectangles]
3) How should we account for the part that is removed and the new surfaces that appear? [find 1/8 of the total surface area and subtract this from the total, then add the area of the two rectangles]