This October, my colleague Rich and I went to the National Numeracy Network annual meeting in Northfield, MN (more on that here). During a session on teaching quantitative reasoning led by the brilliant Kate Folliette, folks shared their favorite brain teasers.
A subset of my favorites are below, and are also currently posted outside of my office (ETC 225). Think through these questions; check the links for more resources/background. (Answers at end of post)