TITLE: Can a rectangle be cut into 5 equal non-rectangular pieces?
QUESTION [5 upvotes]: How to prove that the only figure of which 3 copies can be used to tile a rectangle is a rectangle?
Is it possible to cut a rectangle into 5 equal (modulo rotations/reflections) non-rectangular pieces, which type of pieces?

REPLY [7 votes]: There is a lot of information about this problem at https://mathoverflow.net/questions/11753