ABSTRACT
In this respect, models that use a rectangular sheet of paper are very interesting. Some can be folded from rectangles of any shape, others from rectangles of only one shape (e.g., the so-called silver rectangle, whose sides are in the ratio of 1 :
√ 2), and some from rectangles whose shape must lie
within a certain range. This very easy folded envelope by Luisa Canovi [1], former president of Centro Diffusione Origami (the Italian origami association), is a wonderful example of a model that gives rise to interesting mathematical questions of various natures and is suitable for students at different levels. It is so easy to fold that even small children can do it, as shown in Figure 1.
