During our Structure unit we made towers out of paper in the shapes of a cylinder, rectangular prism and triangular prism.  We then came up with a testable question as a group to see which tower would hold the most weight.  Students then predicted which tower they thought could support the most weight.  The two prisms each held around 14 - 16 chapter books while the cylinder held 49.  Most students predicted the rectangular prism would be the strongest because it is shaped like a house.