## Archive for August 31, 2012

### A Muppet You Can Count On

A big MJ4MF thanks to Lindsey Witcosky, who directed me to a wonderful BBC article about one of my favorite Sesame Street characters, the Count! The link to the article is provided below, but first a quiz based on some trivia in the article.

1. What was the Count’s full name?

2. What was the Count’s favorite number?

3. Who was the voice of the Count from 1970 until 2011?

Answers are below, but you can also find them in the BBC article:
http://www.bbc.co.uk/news/magazine-19409960

The Count’s favorite number is equal to 1872, and BBC Radio asked listeners of the show More or Less to speculate why. One listener noted that 187 = 942 ‑ 932 and, of course, 187 = 94 + 93. The BBC article referred to this coincidence as, “An embarrassment of riches!” But I prefer to think of it as, “An embarassment of algebra!”

Algebra can be used to show why this is true. The nth square number is equal to the sum of the first n positive odd integers. That is,

n2 = 1 + 3 + 5 + 7 + … + (2n ‑ 1)

From this it follows that

942 = 1 + 3 + 5 + 7 + … + (2 × 94 – 1)

and

932 = 1 + 3 + 5 + 7 + … + (2 × 93 – 1)

so of course

942 – 932 = 2 × 94 – 1 = 187

Moreover, the difference of two squares is equal to the product of the sum and difference of the two numbers. That is,

a2 ‑ b2 = (a + b)(a ‑ b)

Consequently,

187 = 942 ‑ 932 = (94 + 93)(94 ‑ 93) = (94 + 93)(1)

So, saying that 187 = 942 ‑ 932 = 94 + 93 is kind of like saying the same thing twice, just in different ways.

1. Count von Count

2. 34,969

3. Jerry Nelson, who passed away on August 23. R. I. P.

### Pringles: The Edible Hyperbolic Paraboloid

My wife forwarded an email with a link to a CNN article and subject line, “Your husband will love this.” Uh-oh. Even my closest friends cannot correctly predict what I will and will not love, so how would a colleague of my wife — who only knows me from an introduction at a professional reception — be able to make such a prediction?

But the article did not disappoint. The author wrote about the mathematically satisfying shape of Pringles®, and she quoted her husband thus:

They [Lays Stax] set themselves up as a Pringles competitor, but it’s an entirely different curvature!

I have never met the author, but her last name was familiar. As luck would have it, her math professor husband and I taught together at a gifted camp for several summers. Small world, eh?

My favorite line of the article was from the last paragraph.

Flavor is subjective. Math is irrefutable.

Fact.

What I enjoyed most about this occurrence was the intersection of several math topics. The article discusses parabolic cylinders and hyperbolic paraboloids, which are topics in multivariable calculus; a colleague of my wife forwarded a link about an article written by the wife of a former colleague, which demonstrates social network theory; and, a colleague of my wife is not equivalent to the wife of my colleague, which shows non‑commutativity.

My two cents? Pringles® rule.

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.