Archive for September, 2012

I’m Only Half-Serious

“I’d like to order a whole chicken,” I said to the man behind the counter at the barbeque restaurant.

“Sorry, dude,” he replied. “We don’t have whole chickens.”

“Oh, okay. Well, what should I get for a family of four?”

“How about two half-chickens.”


So I wrote a letter to the manager at Red Hot & Blue:

To Whom It May Concern,

Please be advised that two halves equal one whole.

A Mathematically Literate Customer

Of course, there are those who could be convinced that 1 = 1/2. Let a = b. Then,

a2 = ab
a2b2 = abb2
(a + b)(ab) = b(ab)
a + b = b
a + a = a
2a = a
2 = 1
2 ÷ 2 = 1 ÷ 2
1 = 1/2

A lot of confusion about halves and wholes occurs in classrooms, too.

Teacher: Who can give me some examples of whole numbers?
Student: 0, 6, 8, 9.
Teacher: What about 10?
Student: That’s only a half-whole, since 1 doesn’t have a hole in it.

September 29, 2012 at 7:36 am Leave a comment

Brew Me a Cup!

Coffee MugInternational Coffee Day is celebrated on September 29, and in the United States the week leading up to it is known as National Coffee Week. This is good news for mathematics. If Alfréd Rényi (or perhaps Paul Erdös?) was correct, then we should defintely see an uptick in the number of theorems produced this week…

A mathematician is a device for turning coffee into theorems.

Should you need caffeine-induced inspiration for the work you’re doing this week, there are plenty of places giving out free cups of joe.

The following corollary is attributed to Paul Turán:

Weak coffee is suitable only for lemmas.

Peter Cameron argues that all math departments should have an adequate supply of the highest possible grade of fuel.

…the effects of coffee (better theorems, more collaboration, more collegiality) are not immediately obvious to administrators, and are not easily quantified (unlike the costs). But they are worth fighting for!

A. J. Tolland is fond of saying, “What we really need is a machine for turning some of those theorems back into coffee.” Kevin Buzzard tells the following story, which seems that this is possible:

Kenneth Ribet once said that he was sent a textbook by a publisher, with the suggestion that he use it in his undergraduate course. He decided not to, and sold it to a second-hand bookstore for a few dollars. On the walk back, he bought some coffee with the money, and then realised to his amusement that he’d done precisely what Tolland had suggested.

And one non-math joke for the week:

Men (or women) are like coffee — the best ones are hot, rich, and keep you up all night!


September 25, 2012 at 11:26 am Leave a comment

11 Comments Caught by the MJ4MF Spam Filter

In Me Talk Pretty One Day, David Sedaris put into words the feeling we’ve all had when trying to speak a foreign language. He wrote:

My fellow students and I engaged in the sort of conversation commonly overhead in refugee camps.

“Sometimes me cry alone at night.”

“That be common for I, also, but be more strong, you. Much work and someday you talk pretty.”

Spam messages with similar grammatical constructs flood the comments section of this blog. Initially, they annoyed me like an ant crawling on my skin — small and insignificant, but causing just enough discomfort that I had to deal with them. Now, however, they’re a source of joy. I read them, chuckle, and then “Delete Permanently,” knowing that my blog enjoys a large enough readership that spammers deem it worthy of their aggravation.

And sometimes, I chuckle loudly.

A number of spam messages have sung my praises:

…thanks on your sweat!

That man can tell what is actually he has been talking about.

Amazing post upon every with the essentials.

Wonderful issues altogether, you simply won a emblem new reader.

This blog was excellent, to say the least. Great piece of literature.

Wow! Great piece of literature? When you think of the greatest literary works of all time — War and Peace, Lolita, Hamlet, The Adventures of Huckleberry Finn — I’m not sure that Math Jokes 4 Mathy Folks would be among them. But, whatever. Ego stroking like that is not only welcomed, but encouraged!

I suspect that spammers think a message of commendation is less likely to be deleted. Perhaps, unless it butchers the English language worse than Balki Bartokomous or includes a link to

One of the recent spam messages was just a little too aggressive for my liking:

Thank you so much, and I am taking a look forward to touch you.

Some are funny because of their poor product placement, like this one:

generic viagra… million a thanks…

I think the spammer was attempting to thank little ol’ me… but it sure looks like he’s thanking a little blue pill, doesn’t it?

And while I don’t know what it means to “bring as much as date” or what the “quite great function” is, I rather appreciated these gems:

I’ll be once more because you bring as much as date.

Fantastic article, gentleman, sustain inside the quite great function.

I’ll anticipate reading by means of much more of your difficult operate.

Finally, the spam filter caught this message, which is grammatically correct:

We are concerned that publication of sacral lecture jokes may endanger the respect to math teachers in freshmen classes.

But I’m confused by the word sacral. It can mean relating to the sacrum, a triangular bone at the base of the spine, or it can mean relating to sacred rites or symbols. I suspect the latter definition was intended here, though I’m unclear of the rite or symbol to which my jokes relate.

For the author of that comment, I have this to say: Chill out, dude.

This is a humor blog, and everything — and I do mean everything — is fair game. I’ve shared jokes about cannibals, gynecologists, inmates, cow tipping, genitalia, and fecal matter, and I’ve made fun of every math profession from statisticians and engineers to physicists and professors. If you can’t see the humor in a joke about a math lecture, then I recommend you find other sites to peruse. You can start with

September 24, 2012 at 11:23 am Leave a comment

12 Math Knock-Knock Jokes

In a very old Second City skit, a man on hold complained (to no one in particular) about the hold music. After his complaint, a voice on the other end of the line said, “I’m sorry. Don’t you like my singing?”

“Who are you?” he asked, surprised.

“I’m your hold operator. If you don’t like music, I’d be happy to entertain you in some other way. Would you like to hear a joke?” she asked.

“Um… sure, why not?”

“It’s a knock-knock joke,” she said. “Are you familiar with the format?”

Now, that’s just funny!

My favorite joke to tell in the classroom is a knock‑knock joke, so I hope that you are familiar with the format.

Knock, knock.
Who’s there?
Interrupting cow.
Interrup — ?

GRiNMy sons are now of an age where they can understand jokes, and those of the knock‑knock variety are told daily in our house. (The knock-knock jokes at GRiN are a source of endless amusement.) Sadly, I didn’t know any knock‑knock jokes that are mathy… so I made some up. Here they are, 12 totally original (sort of) but not terribly funny math knock-knock jokes. Aren’t you glad you stopped by today?

Knock, knock.
Who’s there?
Lemma who?
Lemma in, it’s raining!

Knock, knock.
Who’s there?
Mode who?
Mode the lawn. What should I do next?

Knock, knock.
Who’s there?
Slope who?
Slope ups should stay on the porch.

Big Dogs

Knock, knock.
Who’s there?
Convex who?
Convex go to prison!

Knock, knock.
Who’s there?
Prism who?
Prism is where convex go!
(Weren’t you paying attention to the previous joke?)

Knock, knock.
Who’s there?
Origin who?
Vodka martini origin fizz?

Knock, knock.
Who’s there?
Zeroes who?
Zeroes as fast as she can, but the boat doesn’t move.

Knock, knock.
Who’s there?
Unit who?
Unit socks; I knit sweaters.

Knock, knock.
Who’s there?
Outlier who?
Outlier! We only let honest people in this house!

Knock, knock.
Who’s there?
Möbius who?
Möbius a big whale!

Knock, knock.
Who’s there?
Tangents who?
Tangents spend a lot of time at the beach.

Knock, knock.
Who’s there?
Axis who?
Axis for chopping, saw is for cutting.

September 22, 2012 at 12:38 pm 1 comment

Stolen Truck Solution

Last week, I posted a modified version of Marilyn Burn’s horse problem, and I asked you to submit your answers. I received 331 responses; thanks for participating! An analysis of the submitted responses appears below, but first, a few comments and several different solutions.

My friend Jeane Joyner of Meredith College uses this problem in teacher and parent workshops. She said:

I have folks move to corners of the room — makes money, loses money, and breaks even. Then each groups selects an ambassador to go to the other groups to see if they can persuade folks to move. Fun!

Without further adieu, here is the answer: The man made $200.

Solution #1: He spent 600 + 800 = $1,400, and he received 700 + 900 = $1,600. That’s a profit of $200.

Solution #2: Assume the man started with $1,000 in his bank account. He bought the truck for $600, so he had $400 left. He then sold it for $700, so his account increased to $1,100. He bought it back for $800, so he had $300 left. When he sold it for $900, his account increased to $1,200. Since he started with $1,000 and ended with $1,200, he made a profit of $200.

Solution #3: Use a number line to show how his amount of money changed.

Truck - Number Line

After the four transactions, he is at +200 on the number line, so he made a profit of $200.

Solution #4: Some people find it confusing that he buys and sells the truck twice. It might be easier to think of him doing these transactions with two different vehicles. For instance, what if he bought a truck for $600 then sold it for $700, and then bought a car for $800 and sold it for $900? It might be easier to wrap your head around that.

Approached that way, his actions represent two separate events. The first time he bought and sold the truck, he paid $600 and sold it for $700. That’s a profit of $100. The second time, he bought it for $800 and sold it for $900. That’s another $100 profit. In total, he made $200.

After I posted the problem, a friend on Facebook asked, “Huh? How is that supposed to be hard?” Edward Early of St. Edwards College responded:

Sadly, I’ll only be surprised if there is a strong consensus for the correct answer. I’ve been teaching math too long to expect that to happen.

Of the 331 respondents, only 325 submitted usable responses. (Chalk this up to bad phrasing on my part. I asked folks to “enter a negative number if he lost money, 0 if he broke even, or a positive number if he made money.” I was meaning for people to enter the amount he lost or made, but some respondents entered a positive number that wasn’t possible in the context of the problem, such as 1 or 12. I think they thought they should enter any positive number to indicate that he made a profit. And one wiseacre responded, “a positive number.” Sorry, not even partial credit for that response!)

Of the 325 usable responses, 228 (70.1%) were correct. Answers from the other 28.9% ranged from ‑600 to 900, with 0 (28 responses) and 100 (47 responses) chosen most often. The chart below shows the distribution of incorrect responses. (Data for 200 has been removed since it overwhelms the others; its bar would be more than four times the height of the next highest bar.)

Truck Responses

The vast majority of respondents (276) were 16 years of age or older. The 49 responses from people age 15 or younger looked like this:

Age Responses Correct Responses
6 1 0
7 1 1
8 2 1
9 4 1
10 4 1
11 1 1
12 4 3
13 15 11
14 8 7
15 9 7

Interestingly, the under‑16 crowd, with 67.3% correct responses, did almost as well as the over‑16 crowd, which had 70.6% correct responses. And for the 11- to 15‑year old subset, an astounding 78.4% of the responses were correct.

From this, we can conclude that these youngsters are smarter than the rest of the population… but of course we already knew that, because teens and pre-teens know everything, right?

September 20, 2012 at 1:00 am 1 comment

Boston or New York — Who’s Smarter?

Sure, Boston is home to Harvard, MIT, and Northeastern, but the following statistic may be the most solid proof yet that Boston is home to the smartest people in the world.

Collectively, the good folks in Boston purchased 213 copies of Math Jokes 4 Mathy Folks during the past year. There are 5 million people in the Boston metro area, which means that less than 2% of the U.S. population is responsible for 11% of my book sales. (Thanks, Bean Town!)

But the math geeks in New York are giving them a run for their money. They bought 182 copies of my book in the last 12 months. Since there really isn’t a Yankees-Red Sox race to follow this year, perhaps the media will be watching to see if New York can earn the title of “smartest city on the planet” by overtaking Boston in sales of MJ4MF.

Boston New York

Okay, maybe not, but that sure is a nice segue to this classic joke with a twist…

A chemist, a physicist, and a mathematician were riding the train through Massachusetts in early autumn, enjoying the changing colors.

As they approached Boston, the chemist saw Fenway park and said, “Look! The baseball players in Boston wear red uniforms.”

“No, no,” replied the physicist. “All that we can conclude from the data is that some of the baseball players in Boston wear red uniforms.”

“Uh, not quite,” said the mathematician. “The correct conclusion is only that baseball players in Boston wear uniforms that are red on at least one side.”

“Actually,” said a man sitting behind them, “I don’t even think you can conclude that much. It’s October — so I don’t think you’re seeing any baseball players in Fenway Park right now.”

And lest all ye Red Sox fans get upset by that, here’s one to poke fun at the other side…

A first grade teacher explains to her class that she’s a Yankees fan. She asks her students to raise their hands if they are Yankees fans, too. Not really knowing what a Yankees fan is, but wanting to be like their teacher, almost all students raise their hands. However, Mary has her hands in her lap.

The teacher asks her why she has to be different. “Because I’m not a Yankees fan,” Mary explains.

“Then, what are you?” asks the teacher.

“Why, I’m a Boston Red Sox fan!” says Mary proudly.

The teacher is a little perturbed. She asks Mary why she is a Red Sox fan.

“Well, my dad is a Red Sox fan, and my mom is a Red Sox fan, so I’m a Red Sox fan, too!”

“That’s no reason!” says the teacher angrily. “If your mom were a moron and your dad were a moron, would you be a moron, too?”

“No, ma’am,” says Mary. “I’d be a Yankees fan!”

September 17, 2012 at 12:19 pm Leave a comment

I’m a Pig!

Well, technically, I’ve been dubbed an Honourable Maths Pig by Kerry Cue, a very fun and funny math lover from Australia who runs the Maths Pig blog. And that’s not hogwash!

Maths Pig-a-Go-Go

Kerry bestowed this honor to me “for services above and beyond the call of math duty and for your outstanding contribution to the field of math humour.” Personally, I didn’t know that math humor was a field unto itself. But I think what Kerry did was so nice, I’m not even going to point out that she added an unnecessary s to the end of maths or that she included an extraneous u in humour.

Read my interview with Kerry to find out how I’d change education, what my favorite subject was, and to hear a few of my favorite jokes.

Sadly, I know only one joke involving pigs, and it’s not very mathy. In fact, the only math is that it involves a number. Here goes.

What do you call a pig with three eyes?

But this is a math jokes blog, so let’s see if I can craft an MJ4MF original math joke about pigs…

Two pigs rob a bank. When caught by the police, they were taken to separate rooms. (Isn’t that funny? Pigs were caught by the pigs!) The pigs were told that they could choose to confess or remain silent.

  • If you confess and your accomplice remains silent, all charges against you will be dropped, and your accomplice will be made into bacon.
  • If you both confess, you will be convicted and locked up for six months in an 8′ × 10′ sty.
  • If you both remain silent, you will serve a one-month sentence on a reduced charge.

You probably recogize this as the classic Piggoner’s Dilemma. So, what happened?

Both went to jail for six months. They squealed on each other.


September 14, 2012 at 1:41 pm Leave a comment

Stolen Truck Problem

Pickup TruckMarilyn Burns is the founder of Math Solutions and the author of ten books for children. She uses exceptional problems to promote reasoning and sense making.

I have often heard that, “Good teachers borrow, great teachers steal.” So today, I am stealing one of Marilyn’s most famous problems. The problem recently appeared in our house — as I was preparing dinner one night last week, my sons were getting rowdy, and I needed a diversion. It’s incredibly wonderful to me that I can get them to settle down by saying, “Hey, wanna solve a math puzzle?” I gave them a modified version of Marilyn Burns’ horse problem, and talking about it kept them occupied for 20 minutes, which was just enough time for me to prepare a chicken and vegetable stir fry.

You can read the problem and submit your answer via the form below. Several solutions to the problem, as well as an analysis of all submitted solutions, will be posted on September 20 at Stolen Truck Solution.

If the form does not appear below, you can read the problem and enter your answer on this form. (Please don’t post your answer in the Comments, though.)

September 13, 2012 at 9:30 am 5 comments

Career Changes

When I give math joke presentations, I bombard the audience with several groan‑inducing puns. When they can take no more, I admit to them that (a) stand‑up comedy is NOT my full-time job and (b) I am not considering a career change. This admission usually provokes a collective sigh of relief from the audience.

I inform them, however, that I have several friends who recently changed careers.

I have a friend who used to be a statistician.
Now she’s a gynecologist.
Her specialty is histerectograms.

I have a friend who used to be a combinatorist.
Now she is a hairdresser.
She works with combs and perms.

I have a friend who used to be a high school math teacher.
Now he’s a densist.
He performs square root canals.

I have a friend who used to be a geometer.
Now he’s a taxidermist.
His specialty is Fourier (furrier) transforms.

I know a former inmate.
He became a poet.
Now he writes converse.

I have a friend who used to be a transformational geometer.
Now he polishes mirrors.
He specializes in reflections.

As you might well imagine, telling an audience about these career‑changing friends usually elicits more groans. Go figure.

I particularly like this joke format, so I’ll offer a challenge to you: Create a joke about a career-changing professional. Feel free to use the form below, use this Google Docs form, or place your joke in the Comments.

September 11, 2012 at 5:46 am 1 comment

Kindergarten Math

Alex and Eli started kindergarten on Tuesday.

At a “Meet the Teacher” event last week, we were told that this is the most kindergarten classes they’ve had at the school. “We had to add another class this year, so we now have eight,” one of the teachers said.

“How many students are in each class?” I asked.

“Twenty-one,” she said, “so it’s really good that we added that eighth class — or else there’d be, like, 26 students in each class!”

I was too polite to tell her that 8 × 21 ≠ 7 × 26.

Today, we had a parent-teacher conference. On the bulletin board in her class was the following chart with student names:

Student Name Chart

Click Image to Enlarge

There are 19 students in the class, and all of them have a first name that that begins with a letter in the first half of the alphabet. There are 3 A’s, 1 B, 3 C’s, 1 D, 2 E’s, 1 I, 3 K’s, 3 L’s, and 1 M.

I mentioned this to the teacher. “I know!” she said. “Isn’t that an amazing distribution!”

Well, yeah, I thought. It’s quite amazing, in fact.

If you assume that names are evenly distributed across the alphabet, the probability that all 19 students would have a first name in the first half of the alphabet is an astounding (1/2)19 = 0.00000002%.

But of course, names are not evenly distributed across the alphabet. I don’t know how they’re distributed, but the first letters of English words are distributed as follows:

First Letter Frequency

Click Image to Enlarge

That means that 52.005% of all English words start with a letter in the first half of the alphabet. If you assume that names follow the same distribution, then the probability doubles to 0.00000004%.

Yup. Still pretty low.

September 6, 2012 at 11:30 pm 3 comments

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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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