Math Teacher's Last Thought

This is a dark joke that plays on the tragedy of a plane crash. The punchline uses the geometric term "pentagon" to make a morbidly funny reference to the shape of the building hit on 9/11. It's a pun on a literal object going through the head and a related reference.

• Pentagon
• Math Teacher
• Teacher
• Crash
• 9/11
• Plane

• I was going to tell a 9/11 joke, but it was really plane.
• What do maths and 9/11 have in common? They both prove two parallel lines can be intercepted by a plane.
• On September 11, 2001, I was in geometry class. On that day, we learned you can remove one side of a pentagon by intersecting it with a plane.
• When does a pentagon only have 4 sides? When a plane hits it.