Archive for February, 2019

When Math Falls into the Wrong Hands

My brother-in-law recently forwarded an email that contained a lot of images plucked from various degenerate corners of the internet, and he suggested that this one could go into my next book:

image of a handwritten note, with a definite integral given as the PIN code for an ATM card

I suppose it’s funny enough, and I guess it’s technically a math joke, but there’s a problem.

It doesn’t work.

I know, I know. Most people just read the joke, get the humor that the note’s author has used some odious expression to represent the PIN code, and go on about their day. Plus, I’ve heard that less than 1% of the world’s population has taken calculus, so there aren’t too many people who could actually check the math. Not to mention, how many of them would care enough to do so?

Uh… I can think of at least one person who cares enough.

Venn diagram with circle for knows calculus, another circle for cares about the math in jokes, and contains the author's image in the intersection

While it’s certainly egotistical to think that I’m the only one in the intersection, it’s likely offensive to include anyone in the intersection who really wouldn’t want to be. So apologies to Matt Parker, Des McHale, Colin Adams, Ed Burger, or any of the other funny math folks who think they should have been included.

Anyway, where was I? Oh, right. Bad math.

The definite integral in the joke sent by my brother-in-law doesn’t yield a four-digit positive integer.

calculation from Wolfram Alpha showing the value of a definite integralIn fact, it yields a very irrational number with a lot of digits:


So unless the PIN code for that bank card has an infinity of digits, well, this is going to be problematic.

I propose, instead, that the joke be rewritten to use the following:

definite integral of x-squared dx from 1 to 19Would it be less funny? Probably. But at least it’d be accurate.

Not to mention, it would be a significantly more fair to Darling. Honestly, no one should ever have to do integration by substitution.

February 25, 2019 at 7:31 am 2 comments

About MJ4MF

The Math Jokes 4 Mathy Folks blog is an online extension to the book Math Jokes 4 Mathy Folks. The blog contains jokes submitted by readers, new jokes discovered by the author, details about speaking appearances and workshops, and other random bits of information that might be interesting to the strange folks who like math jokes.

MJ4MF (offline version)

Math Jokes 4 Mathy Folks is available from Amazon, Borders, Barnes & Noble, NCTM, Robert D. Reed Publishers, and other purveyors of exceptional literature.

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