Puzzles that fool the eye
Chessboard paradox
Cut an 8 × 8 square (64 squares) into four pieces, and they make a 5 × 13 rectangle (65 squares). Where does the extra square come from?
There is a very thin gap along the long diagonal.
Why? The pieces don’t quite fit: along the long diagonal there is a very thin gap, exactly one square in area.
Picture: Yoni Toker, CC BY-SA 4.0 · Wikipedia(opens in a new tab)