Math Jokes for Halloween

Tom Lehrer said, “Base eight is just like base ten, really… if you’re missing two fingers!”

Ever notice that cartoon hands only have four fingers? There’s a very simple reason for that — it’s easier to draw a hand with four fingers than with five fingers. But have you ever wondered what it would be like to have only four fingers on each hand? For one thing, you’d count in base eight, not base ten. For another, you’d never be able to give someone a high five.

Base eight and base ten are relevant to a math joke that’s appropriate for today:

Why do mathematicians sometimes confuse Halloween and Christmas?
Because Oct 31 = Dec 25.

It’s a wonderful coincidence that October 31 and December 25 both happen to be days with significance, which is why that joke works. It’s no coincidence, however, that the abbreviations for October (Oct) and December (Dec) could also be the abbreviations for the octal (base 8) and decimal (base 10) number systems. In the old Roman calendar, October was the 8th month, and December was the 10th month. When the Julian calendar was created, July and August were added in the middle of the year, pushing October and December to the 10th and 12th slots, respectively.