## Archive for September, 2011

### 5 (or Maybe 6) More Math Jokes

I asked an actuary to calculate the number of jokes that have been posted on the MJ4MF blog.

He replied immediately and definitively, “1005.”

“Wow, how did you count them so fast?” I asked.

“Well, there are 5 jokes below,” he said, “and about a thousand in the archives.”

The young math professor had not had a paper accepted for publication in almost four years. Feeling a little discouraged, he considered quitting and becoming a fisherman. But he quickly realized that he wouldn’t be able to survive on his net income.

The surgeon asked a heart transplant patient, “What kind of heart would you like to receive?”

“How about one from a statistician,” the patient says. “That way, I’ll know it’s never been used.”

What’s the difference between an actuary and an accountant?

About $50,000.

If you took all of the actuaries in New Jersey and laid them end-to-end on the NJ Turnpike… would anyone care?

Feeling a little hungry,

f(x) =x^{2}+ 3 walks into a restaurant. “Got any sandwiches?” he asks.“Sorry,” says the waiter, “we don’t do catering for functions.”

### All Sorts of Antics

It’s hard to describe the emotion I felt after writing this post…

Read on. You’ll see what I mean.

What do you call an insect who skips school?

Truant.What do you call two insects who change simultaneously?

Covariants.What do you call an insect pursuing a degree in mathematics who lives in on‑campus housing?

Dormant.What do you call an insect on an inclined plane?

Rampant.What do you call an insect who does your taxes?

Accountant.What do you call an insect who lives on the outside of a sphere?

Exorbitant.What do you call an insect who occupies the middle position in a long line of insects?

Mediant.What do you call an insect who is completely committed to passing linear algebra?

Determinant.What do you call an insect who can easily recognize the number of real roots for an equation?

Discriminant.What do you call an insect whose shape remains unchanged when reflected?

Flippant.What do you call an insect who is always looking for things?

Secant.

### 4 Jokes, Just For Fun

A random compilation of four unrelated jokes, just for fun…

Two math professors are exiting the subway when a panhandler asks them for some change. The first prof refuses in disgust. The second prof, however, opens his wallet and gives him a $5 bill. “What’d you do that for?” asks the first. “You know he’s just going to use it for booze.”

“And we weren’t?” says the second.

What do statisticians use for birth control?

Their personalities.

Three engineers on a desert island find a magic lamp. They rub it, and a genie pops out. “I’ll grant you each a wish,” says the genie.

The first engineer says, “I wish I had 25% more intelligence. Then I’d be smart enough to get off of this island.” The genie turns her into an accountant, and she swims off the island.

The second engineer watches this and says, “I wish I had 50% more intellignce. Then I’d be smart enough to get off this island.” The genie turns her into a statistician, and she makes a raft from trees and sails off.

Finally, the third engineer says, “I wish I had 100% more intelligence. Then I’d be smart enough to get off this island.” The genie turns her into a mathematician, and she walks across the bridge.

What’s the difference between a dead skunk in the road and a dead economist in the road?

There are skid marks before the skunk.

### Bad Analogies Are Like Bananas in a Swordfight

The word *analogy* derives from the Greek word *analogia*, which means “proportion.” An analogy is a comparison of two things, and a good analogy is like an elegant proof — it may require numerous false starts, but the end result is usually worth the effort.

Here are two of my favorite analogies:

Long separated by cruel fate, the star-crossed lovers raced across the grassy field toward each other like two freight trains, one having left Cleveland at 6:36 p.m. traveling at 55 mph, the other from Topeka at 4:19 p.m. at a speed of 35 mph.

The politician was gone but unnoticed, like the period after Dr on a Dr Pepper can.

The wonderful analogies above originally appeared in the Style Invitational, a weekly wordplay contest in the Style section of the *Washington Post*, through which its creators “seek to bring a variety of clever, timely, irreverent humor” to readers every week. Incidentally, the analogies above were responses to the Style Invitational on Pi Day 1999. They are not — as often purported on numerous plagiaristic websites and in various irreputable publications — pulled from high school essays. They are works of comic genius, not examples of poor writing by ill-informed teen-agers. The freight train analogy was penned by Jennifer Hart of Arlington, Virginia, and Wayne Goode of Madison, Alabama, deserves credit for the unadulterated brilliance of the Dr Pepper analogy.

Of course, analogies are not for everybody. For instance, the Alabama geometry teacher who used an analogy of shooting President Obama when teaching parallel lines and angles should probably consider a different example. While such a story may make you smile, it’s not really funny.

But analogies can be humorous, such as the following joke from Calamities of Nature:

Yo mama is such a slut that the set of guys she’s slept with has cardinality aleph-naught!

At least it’s not aleph-one!

In the comments section for that cartoon, one astute observer noted:

Well, it couldn’t be aleph-one unless she could manage at least aleph-naught at a time (amazing) or the encounters were amazingly brief.

I greatly appreciate when the comment on a web comic is funnier than the cartoon itself!

Finally, here’s my all-time favorite analogy, which compares two things not typically seen as similar:

Writing this post was like driving across the George Washington Bridge during rush hour — it took a lot longer than I had hoped, but at least I didn’t get wet.

Like I said, analogies aren’t for everyone.

### Moebius Noodles Project

My friend Maria Droujkova of the Natural Math Project has taken on the task of building a Creative Commons book and support site for parents who want to enjoy math with their young kids (ages 0 to 5 years).

As a parent who loves to play math games and talk about numbers and shapes with my twin 4-year-old sons (see my previous post), I believe this effort is laudable. I support the project, and I would like to ask for your support, too.

### Wee Wee Can-Can Doodoo KenKen

My sons love words with repeating syllables, such as…

*pee pee**poo poo**knock knock**bam bam**Pop Pop**couscous*

But, by far, their favorite word that exhibits exact reduplication is KenKen.

My friend Harold Reiter creates KenKen puzzles. His aren’t the garden-variety, generated-by-computer-algorithm type, though. His puzzles have interesting features, such as including the first initial of his name as one of the cages:

Note that the puzzle above also has a “clueless cage” in the upper right corner; to solve the puzzle, it is not necessary to know the value or operation associated with this three-square cage. (If KenKen is new to you, check out the rules for solving.)

On a recent rainy afternoon, my twin four-year-old sons Alex and Eli solved the puzzle above. On their own, they identified the set of seven numbers that could uniquely fill the H. Eli said, “I know that 8 × 6 = 48, and 8 = 4 × 2 and 6 = 3 × 2, so it’s {1, 1, 1, 2, 2, 3, 4}.” I asked if there were any other possibilities. Eli continued, “Well, 1 × 1 × 2 × 2 × 2 × 2 × 3 = 48, too, but there can’t be four 2’s, because there are only three columns in the H.” I then had to help with some of the logic about how to place those seven numbers… but once they realized that the center of the H had to be a 1, they were off to the races.

After completing the puzzle, I told Alex and Eli that my friend Harold had created the puzzle. Upon hearing this, Alex turned the paper over. “Let’s make a KenKen puzzle,” he suggested. And why not? I drew a 4 × 4 grid for them, and they proceeded to tell me where to place the digits to create a Latin square. Then, they indicated the location of the cages, as well as the values and operations to use within the cages. To prove that the solution was unique, I created a blank version of the puzzle on a different sheet of paper. When I asked the boys to solve it with me, Alex grabbed the paper on which we had originally designed the puzzle and showed me the solution. (Okay, so maybe they don’t yet understand the concept of uniqueness, but I appreciated Alex’s application of a fundamental problem-solving strategy: reduce it to a previously solved puzzle!)

For your enjoyment, I present Alex and Eli’s first-ever KenKen puzzle.

If you roll your mouse over the puzzle above, you’ll notice the alternate text reads, “Alex and Eli’s KenKen Puzzle for Grandma.” Upon completing the puzzle, the boys suggested that we send the puzzle to their grandmother. So we did. That was over a week ago… and we still haven’t heard a response.

### Math Fortune Cookies

Today might be Fortune Cookie Day. Hard to say, really, because there are also plenty of references on the web that claim July 20 is Fortune Cookie Day, and the good folks at Holiday Insights claim that there are references to a Fortune Cookie Day in April, May and June, too. But honestly, who cares? No one should lose sleep over an incorrect date for a made-up holiday.

Besides, if you can accept that today is Fortune Cookie Day, well, that gives me a good reason to now tell you two fortune cookie stories.

The first concerns the publication of *Math Jokes 4 Mathy Folks*. About an hour after Bob Reed called to tell me that he’d like to publish my book, I was dining at a Chinese restaurant. The fortune in my cookie read: *Your current plans will succeed*. Though I am unwilling to ascribe the success of a book to a fortune cookie, the fortune appears to have been true. Since publication on August 9, 2010, more than 5,000 copies of *MJ4MF* have been sold. Though I am still holding out hope that it will sell a million copies, I cannot be disappointed in a book of math jokes that reaches 5,000 people.

The second story involves my friend Andy Fielding. The day before he left for Africa to serve two years in the Peace Corps, he and I were dining at a Korean restaurant. After the meal, two fortune cookies were placed on the table. I told him to select one. “No, no, you first,” he insisted.

“But you need the good luck,” I said. “You’re leaving tomorrow.” He repeatedly refused, and the argument continued for 20 minutes. “Oh, fine!” I said finally, and took one. The fortune: *You are about to take a long and safe journey*. “Dammit,” I said as I showed it to Andy. “This was meant for you!”

“It’s okay,” he said as he showed me his fortune, which read: *You are about to take a long and safe journey*.

Someday, I hope to open a Chinese restaurant. The portions will be very large, and the existence of leftovers is guaranteed by the Chinese Remainder theorem.

When I do, I look forward to generating creative fortunes to place inside the cookies. Here are a few. (Feel free to add to this list by posting your favorite fortunes in the comments section, or get creative and write one of your own.)

- You are a complex person, and
*i*would like to be your friend. - When life throws you a curve, calculate the slope of the tangent at the point of inflection.
- You will live a long life. If you marry an actuary, it will feel even longer.
- Some day you will find a useful application for Ceva’s theorem. (Maybe.)
- Your lucky number is the square root of 17.
- Fame and fortune will find you… unless you lock yourself in an attic, trying to prove the Riemann Hypothesis.
- Will you still need me, will you still feed me, when I’m 2
^{6}? - I have found an elegant proof of Fermat’s Last Theorem, but this fortune is too small to contain it.
- You are good at solving problems. Textbooks fear you.
- This cookie contains no fortune.
- Your students secretly agree that your head is not in proportion to your body.
- A foolish man will try to write a better fortune than this, but a mathematician will find it sufficient to know that a better fortune exists.
- When someone finds a counterexample to your proof, look for a different proof.
- A conclusion is your last thought before you got tired of thinking.
- You are so smart that you do not need answer keys.
- The fortune of this cookie is obvious.
- You are good at geometry. Q.E.D.
- Greet new friends with a handshake. At a math social, greet new friends with the handshake problem.
- Do not follow the instructions in this fortune cookie.
- Do not kiss a mathematician on the lips. Ever.

### Jokes In Order

“Daddy,” said Eli, “there’s a new math joke we need to tell you.”

“Really?” I said. “Where did you hear this joke?”

“I made it up,” Eli said.

“Well, then, let’s hear it!”

What did 0 say to 10?

Nice one!

Okay, so maybe it’s not a knee-slapper… but I still think it’s pretty cool that my 4-year-old son created a math joke.

I especially liked that he made up his joke about 10 on the 10th of September; more specifically, on the sequential date 9/10/11. Here’s a joke about sequences:

Being without you is like being a metric space in which a Cauchy sequence exists but does not converge.

The date 9/10/11 is also interesting in Roman numerals — it is IX/X/XI, which is a palindrome. How many other sets of three consecutive Roman numerals, when taken in order, form a palindrome?

### 18 New Math Terms for Lingweenies

Have you met a mathemagician? Even if you haven’t, you’ve no doubt heard this neologism that many math educators are using to descirbe themselves.

**math·e·ma·gi·ci·an**

*noun*

1. a mathematician who practices magic

2. a mathematician or math educator who thinks that what he does with numbers is magical

3. a person who believes that neither doing magic nor doing math is, by itself, quite dorky enough

I love words, and I love math. But personally, mathemagician is a neologism I could have done without.

On the other hand, there are some coined words that deserve special praise. Rich Hall is the undisputed king of neologicians — in the mid-1980’s, Hall hosted a segment on the monthly HBO series *Not Necessarily the News* entirely dedicated to *sniglets*.

**snig·let**

*noun*

any word that doesn’t appear in the dictionary, but should

Hall coined many sniglets, and viewers of the show submitted others. Sniglets became so popular that they led to five books (one for children), a game, and a sniglet-a-day calendar.

My favorite sniglet was *mega-nega-bar*.

**meg·a-neg·a-bar**

*noun*

the line you put after the written amount on a check, to prevent someone from adding “and one million dollars”

Though not one of Hall’s sniglets, the following self-referential neologism deserves a gold star, too.

**ling·wee·nie**

*noun*

a person incapable of producing neologisms

Why all this talk of made-up words? You can blame the good folks at the The Daily Post, who presented Topic #230:

Make up a word and its definition.

Admittedly, this post comes a few days late, as the 230th day of the year was August 25. But the topic is one worth exploring, as there are many new terms that aren’t in math dictionaries, but perhaps they should be. (Or maybe not.)

The following list contains neologisms that you should feel free to use in daily conversation and at cocktail parties, especially if your audience consists of people who understand the statement, “The kernel of the adjoint of a linear transformation is both the annihilator space of the image of the transformation and also the dual space of the quotient of the space of which the image is a subspace by the image subspace.”

**mal·e·frac·tion**

*noun*

an illegal mathematical move when working with rational numbers, such as dividing by 0 or assuming that*a*/*b*+*c*/*d*= (*a*+*b*)/(*c*+*d*)**in·fin·ish**

*adjective*

almost, but not quite, without bound**trig·gle**

*noun*

a laugh that follows a joke in trigonometry class, like when the teacher asks, “What is the sine of 40?” and a student responds, “Saying things like, ‘When I was your age…'”**Mö·bi·us trip**

*noun*

a vacation that only requires a one-way ticket**bi·sec·tu·al**

*noun*

a person who divides things into two parts**tan·gen·tle·man**

*noun*

a learned male who has frequent digressions**al·ge-ca·da·bra**

*noun*

the exclamation made before the magical moment of solving an algebra problem**win·ter·val**

*noun*

any period of bitter coldness, such as September through July in North Dakota**phe·nom·i·na·tor**

*noun*

any of the recurring numbers that often serve as least common denominators, especially the two-digit numbers 24, 36, 48, 72, and 96 that appear regularly in the answers to fraction exercises of middle school math textbooks**pter·a·frac·tal**

*noun*

a self-similar geometric shape that has become extinct (or is, at least, out of fashion)**com·mo·di·an**

*noun*

the common value of the mode and median in a data set (for sets in which the mode and median are equal)**tri·gan·gle**

*noun*

a group of three-sided objects**con·triv·i·al**

*adjective*

friendly and jovial but also irrelevant**per·pen·dic·u·lous**

*adjective*

deserving of contempt because it feels so right**squad·rant**

*noun*

a math department consisting of 600 geometricians**re·cip·ro·cool**

*adjective*

containing enough awesomeness that it makes you flip**neo·log·a·rith·m**

*noun*

a new math term**mon·gro·nom·i·al**

*noun*

an unfriendly algebraic expression involving only one term, such as 323*u*^{2 }*g*^{3 }*l*^{5 }*y*^{7}

Of course, no list of new words would be very effective without examples. The following sentences use several of the neologisms above.

Just before dividing his assistant in two, the bisectual mathemagician proclaimed, “Alge-cadabra!”

Though a contrivial tangentleman, the senior member of the squadrant often threw perpendiculous parties.

It’s not uncommon for students to commit malefractions, especially when a problem does not involve a phenominator.

### Labor Smarter

There is debate as to whether Carl Banks, creator of Scrooge McDuck, or Christopher Thomas originally coined the following phrase.

Work smarter, not harder.

Regardless of the author, it seems a good quote to keep in mind on Labor Day, and I was reminded of it when my sons were solving mazes yesterday. I thought they might enjoy learning a little theory that would make solving a maze easier, now that they’ve gotten quite good at completing mazes with brute force.

Before sharing with you what I shared with them, here are two maze-related jokes.

The first is a maze for liberal arts majors, who always seem to have trouble finding their way.

The second is a maze I call *Good Frickin’ Luck*.

With those out of the way, on to the theory of mazes.

For simply connected mazes — that is, those mazes for which every wall is connected to either another wall or to the boundary — solving the maze can be accomplished by coloring the walls with just two colors. That’s because such mazes consist of two disjoint parts, and the solution path lies between those two parts.

Consider the simple maze below, which, by the way, I created “on the spot” for my sons when they had completed all the mazes in their activity books.

You can then color all of the connected walls on the top half of the maze red, and you can color the other walls blue. This gives the following result, and the solution is the path that lies between the red and blue halves, as shown.

My kids thought that was pretty cool. Hope you did, too!