Optical Illusion of the Extra Piece
Rearrange the five polygons to create another rectangle that appears to have the same dimensions even without the brown piece. However, the final rectangle shrinks slightly in the direction by an area equal to that of the brown piece. This illusion is commonly referred to as "The Chocolate Bar Illusion."
This was a project for Advanced Topics in Mathematics II, 2016–2017, Torrey Pines High School, San Diego, CA.