All the challenges in this entertaining puzzle book are the same. Fold the corner of the paper to a given dot and find the folded area. A small move of the target dot can drastically change the logic needed to find the solution to the challenge. The problems become increasingly complex as the book progresses, with possible solutions involving Pythagoras' and similar triangles as well as trigonometry and algebra. However, insights learnt from earlier challenges can help with those that follow. If at any point the challenge becomes too great, the answers can always be found by measurement with...