## Archive for September, 2010

### Math Clocks

Jiminy. The folks at Clock Zone make a math class wall clock — and I would like to be the first to publicly chastise buy.com, amazon, and anyone else who is selling it. It contains at least two mathematical errors:

SPOILER ALERT: In my rant below, I identify the errors in the clock. If you’d like to identify them for yourself, don’t read any further.

I say “at least” two errors because there may be more. The obvious errors are for 9 (the expression assumes that the exact value of π is equal to the common approximation 3.14) and for 7 (because the equation is quadratic, *x* = 7 is only one of the answers; the other possible answer is *x* = ‑6).

More generally, I have an issue with any of the algebraic equations that are meant to represent integers. For instance, the equation 50/2 = 100/*x* has solution *x* = 4, but I believe that it is incorrect to say that the equation itself is equal to 4. So perhaps the clock has four errors, if you consider the algebraic equations for 4 and 10 to be erroneous, as I do.

This clock is meant to be a math joke. Edward de Bono in *The Mechanism of the Mind* (1969) suggested that when a familiar connection (such as seeing the numerals 1‑12 on a clock) is disrupted, laughter occurs as a new connection (seeing mathematical expressions instead of numerals) is made. Sadly, math jokes are supposed to make you laugh… yet this clock makes me want to cry.

To ease the pain, I did a little research and uncovered several clocks of famous mathematicians. I present them here for your enjoyment.

Leonardo da Pisa:

Kenneth Appel:

Rene Descartes:

Karl Friedrich Gauss:

### Rhyme Time

My friend Josh Zucker created a joke about math and poetry:

Why don’t 8 and 15 make good poets?

Because they only relatively rhyme.

Painful, I know. Hopefully the following poems will ease the hurt.

The first poem yields a system of equations in two variables. I can tell you that using algebra is not so easy, but I was able to find the solution in about four minutes with an Excel spreadsheet.

Take five times which plus half of what,

And make the square of what you’ve got.

Divide by one-and-thirty square,

To get just four — that’s right, it’s there.

Now two more points I must impress:

Both which and what are fractionless,

And what less which is not a lot:

Just two or three. So now, what’s what?

The following poem by Leo Moser poked fun at Paul Erdös’ tendency to publish important proofs in obscure journals.

A conjecture both deep and profound

Is whether a circle is round.

In a paper of Erdös,

Written in Kurdish,

A counterexample is found.

And one of my favorites from Shel Silverstein:

My dad gave me one dollar bill,

‘Cause I’m his smartest son.

And I swapped it for two shiny quarters,

‘Cause two is more than one!And then I took the quarters

and traded them to Lou

For three dimes — I guess he doesn’t know

That three is more than two!Just then, along came old blind Bates,

And just ’cause he can’t see,

He gave me four nickels for my three dimes,

And four is more than three!And I took the nickels to Hiram Coombs

Down at the seed-feed store.

And the fool gave me five pennies for them,

And five is more than four!And then I went and showed my dad,

And he got red in the cheek.

He closed his eyes and shook his head —

Too proud of me to speak!

### Confounding Factors

My colleague Julia is preparing a talk about factoring for an elementary audience, and she created the following problem to use as a warm-up:

Take a two‑digit number

ab, and find the least common multiple ofa,b, andab.For example, if you take the number 35, then LCM(3, 5, 35) = 105. For which two‑digit numberabis LCM(a,b,ab) the greatest? (The notationabis used to indicate the two‑digit number with tens digitaand units digitb, which is equal to 10a+b. This notation is used to distinguish the two‑digit numberabfrom the productab.)

Here are some math jokes about factors:

What do you call an amount that exactly divides a recipe for a sweet confection?

A fudge factor.What do algebra equations and British television have in common?

An X Factor.

Sadly, both of those are my original jokes. Sorry. To cleanse your palate, check out one of Randall Munroe’s original jokes about factoring:

### NCTM Regional Conference in Denver

The NCTM Regional Conference in Denver, Colorado, will be held October 7-8, 2010. I’ll be presenting two sessions at the conference:

**Developing Geometric Thinking**(Grades 6‑8), Thursday, October 7, 12:30‑1:30 p.m., Colorado Convention Center, Korbel 4C- Illuminations (illuminations.nctm.org) offers free resources that develop geometric reasoning skills. The Tessellation Creator allows students to explore patterns with polygons. Paper Pool requires students to consider similar figures in context. Several other Illuminations lessons in geometry will be examined.

**New and Preservice Teachers Workshop**, Thursday, October 7, 10:30 a.m.‑12:00 p.m., Colorado Convention Center, Korbel 4B

If you happen to be in Denver the same weekend, please stop by and say, “Hi!”

### Northwest Math Conference

The 49th Northwest Math Conference will be held October 7-9, 2010, in Spokane, Washington. I’ll be one of the featured speakers, and I’m both proud and intimidated by the company I’ll be keeping. I’ll be presenting three sessions at the conference:

**Engaging (and Free) Online Resources for the Secondary Classroom**, Friday, October 8, 1:30‑2:50 p.m., Room C‑206C**Engaging (and Free) Online Resources for the Elementary Classroom**, Saturday, October 9, 8:00‑9:20 a.m., Room D‑Salon I**Math Jokes 4 Mathy Folks**, Saturday, October 9, 9:30‑10:20 a.m., Room D‑Salon I

If you’ll be in eastern Washington the same weekend, please stop by and say, “Hi!”

### All About Cannibals

Last weekend, I presented my Puns and Puzzles workshop at Reiter’s Books in Washington, DC. During the talk, I told the audience my favorite non-math joke, which I’ve posted on this blog before. But it’s worth repeating…

Two cannibals are eating a clown. One says to the other, “Does this taste funny to you?”

While at Reiter’s, Umar Khan, the organizer of the Washington, DC, math meet-up group, offered the following modification:

Two cannibals are eating a video programmer. One says to the other, “Does this taste gamey to you?”

Inspired by Umar’s modification, I posted the joke to Facebook and asked if anyone else had a modification. To my surprise, it started a firestorm! Here are some of the best replies:

Two cannibals are eating a mathematician. One says to the other, “Does this taste odd to you?” (Beth Dare)

Two cannibals are eating Jennifer Aniston (double entendre intended): “Does this taste bitter to you?” (June Bretz Jebram)

Two cannibals are eating a deep sea fisherman. “Does this taste salty to you?” (Amy Bucci)

Two cannibals are eating a coward. One says, “Does this taste like chicken to you?” (Dave Sundin)

And my friend Ayal Cohen couldn’t resist the opportunity to make fun of me directly:

Two cannibals are eating a math joke book author. One says to the other, “Why was 10 afraid of 7? Because 7 8 9!” No, wait, that’s not right. One says to the other, “Man, that was a tasteless joke.” Wait wait, hold on… the punch line is coming. Two cannibals are eating Patrick Vennebush. One says to the other, “Did you know he published a math joke book?”

“Huh?” says the other. “Who is Patrick Vennebush?”

Finally, Beth Dare offered a cannibal joke that doesn’t fit the format… but since it makes fun of several math professions, it’s worth sharing, too.

Five cannibals are hired as engineers at a defense company. The boss welcomes them, tells them they have complete access to the cafeteria, but asks them not to bother the other employees. Four weeks later, the boss congratulates them for their hard work, but he also says that the janitor is missing. “Do any of you know what happened to him?” the boss asks. None of them says anything, and the boss leaves.

When the boss is out of earshot, one of the cannibals says, “Okay, which of you idiots ate the janitor?” Meekly, one of them raises his hand. “You idiot!” shouts the first. “For a month, we’ve been eating accountants, statisticians, mathematicians, engineers, project managers and supervisors, and no one noticed! But you had to go and eat the janitor!”

### Three Jokes from Italy

Thanks to Maurizio Codogno, who bought my book from bookdepository.co.uk (they were kind enough to ship it to him in Italy), and who also shared a few jokes that weren’t in *Math Jokes 4 Mathy Folks*. Enjoy them, hot off the presses from Milan!

**Question and Answer**

Q: What is the difference between a mathematician and a physicist?

A: The mathematician thinks there is only one straight line that passes through two points; the physicist, however, needs more data.

**Logic Exam**

A student asks his logic professor, “Sir, did I pass or fail the exam?”

The professor replies, “Yes.”

**Quantum Mechanics**

Every Friday night, a mathematician goes to the pub, sits on the next-to-last stool, turns to the last stool, and asks to a non-existent woman if she would like a drink. The mathematician returns every Friday night for a year, yet the bartender says nothing.

Finally, the last Friday before summer break, the bartender asks the mathematician, “Excuse me, sir. You are clearly aware that there is no woman sitting in that chair. Why do you keep talking to an empty stool?”

The mathematician responds, “According to quantum mechanics, an empty space is not really void. Virtual particles materialize and disappear at every instant. Nobody knows whether the appropriate wave function collapses in such a way that a beautiful girl will appear out of nowhere.”

The bartender raises his eyebrow. “Really? That’s interesting. But couldn’t you just ask one of the women already in the bar if she’d like a drink? Who knows, maybe one of them would say yes.”

The mathematican laughs. “Oh, sure!” he says. “And what is the probability of

thathappening?”

### A Funny Phone Call

Deborah Bliss is a former vice-president of the Association of State Supervisors of Mathematics and the current Instructional Supervisor for Mathematics in Loudoun County Public Schools (VA). During a recent phone call, she shared two jokes with me that are worth passing on to others.

Why did 1/5 need to visit the school counselor?

Because he was two-tenths (too tense).

The second joke is actually more of a story.

The Association of State Supervisors of Mathematics (ASSM) holds an annual conference. One year when Deborah returned from the conference, she brought home one of the conference give-aways, a tote bag with the ASSM logo on it. Upon seeing this, her daughter exclaimed, “Mom, it’s an ASSM tote!” (asymptote).

### A Nice (and Funny) Note

Professor Francisco Craveira de Carvalho from the math department at Universidade de Coimbra recently sent me two jokes.

Teacher: “… and this concludes the proof. PLOP!”

Student: “What was that?”

Student: “It’s his vocal version of the Halmos symbol.”

The *Halmos symbol*, which is also known as the *mathematician’s tombstone*, is a little black square (■) used to indicate the end of a proof. Named after mathematician Paul Halmos, it was created by Donald Knuth to be used in TeX to replace Q.E.D. when typesetting mathematics.

His second joke was graphical.

But most importantly, Professor Craveira sent me a message —

I bought your book in NY. Great fun! Congratulations!

— about which I was very excited! Despite its brevity, the message contained much information. Specifically,

- It proved that someone had actually read the introduction to
*Math Jokes 4 Mathy Folks*. (PLOP!) - Even if others had read the introduction, this was the first time someone used the email address in the introduction to send me a message.
- Professor Craveira told me that he bought my book at a Barnes & Noble on Fifth Avenue. To my knowledge, this is the first brick-and-mortar purchase of
*MJ4MF*.

Professor Craveira’s brief message of just 45 characters (not including spaces) made my day. Thanks, Professor Craveira!