April Fool’s Day: Fun with Math Fallacies

Photo by RBerteig. Take a break from “serious” math and have a little fun today with some classics of recreational mathematics. Do you have a favorite math or logic fallacy? Please share it in the Comments below.

Story Problem Fallacy

• Three Men in a Hotel Room From the comments section at Let’s Play Math! blog.

Algebra Fallacies

• Classic Fallacies Can you find the false step in each of these “proofs”?
• How to Double Your Salary Using an Algebraic Loophole Another version of the beginning algebra fallacy, from WikiHow.

Geometry Fallacies

• Dissection Fallacy 63 = 64 = 65 from WolframMathWorld.
• What Is Wrong? (Rouse Ball’s Fallacy) A geometry “proof” from Cut the Knot.

Edited to Add

I found this spoof of a famous number theory joke in my feed reader this afternoon…

• Proof: all April fools’ jokes are interesting “Let S be the set of uninteresting April fools’ jokes…”