We promote math knowledge and understanding with situations, anecdotes, jokes, photos, videos and anything else that will make you smile, laugh, think and enjoy things mathematical.

In her YouTube video, Amelia entertains us by turning her body with dance into a mathematical visual aid. She also demonstrate the endless ways one can present mathematical concepts.

Visiting family in Kentucky is a heart-stopping experience if only because my brother-in-law drives in the middle of the road, straddling the double
yellow lines that separate traffic. My sister-in-law does little to ease my fears. Seeing the horror in my eyes, she once said, “Don’t worry. Everyone around here drives in the middles of the road.”

Lisa Walters, Ypsilanti, Michigan

[Source: Reader's Digest, June 2009, Life (p. 198)]

Well, here is a story that has stuck in my head for many years. I may be off on the specifics but I believe the just of it is true. And, if not, it could have happened or, in storytelling parlance, its plausible.

As I recall, in the mid 1960s in Israel I read in the paper that a shipment of 10,000 left shoes had arrived in the port of Haifa from Italy. At the time, custom duty rates in Israel were extremely high, especially on such luxury imports. So the importer did not claim the shoes. Besides, what would he do with 10,000 left shoes? Stuck with this load, the custom office did what most custom agencies do with abandoned stuff, it auctioned it off. But no one had any use for 10,000 left shoes so no one made any bid. Well, eventually the original importer made a very low bid and the custom office was happy to get rid of the shoes that took space in its warehouse. So the importer got his 10,000 left shoes practically paying no duty.

A month or two later a shipment of 10,000 right shoes arrived in the port of Haifa and the same importer did not claim them because he did not want to pay the duty

Surely, you have figured out by now the rest of the story.

Where is the math in this story?

It has to do with sets and how sets can be split, added up and rearranged. A pair of shoes is a set, a very useful set. It can be sold. 10,000 pairs is a set of 10,000 such useful sets. Splitting these pairs into 10,000 left shoes and 10,000 right shoes generates 2 sets containing 10,000 of useless shoes, which no one wants to buy. But then, whoever has both sets can recombine them to form the original 10,000 sets of sellable pairs of shoes.

A student returned home from a date at 3 AM. Her parents were very upset, “You’re late! You said you’d be home by 11:45!”
“Actually,” the girl replied, “I’m right on time. I said I’d be home by 1/4 of 12.”

[Origin: unknown; several variations of this joke appear on various web; a version of this joke, submitted by Zhang Wenyi, was published in Reader's Digest, July 2009, "Laugh!:)", p. 27]

For the unfamiliar, there is a class of jokes about how awesome Chuck Norris is. Here I will post those with mathematical twist.

Chuck Norris counted to infinity, twice.
[www.chucknorrisfacts.com, as of 2009-02-22]

Chuck Norris knows the last digit of pi.
[www.chucknorrisfacts.com/page8.html, as of 2009-02-22]

Chuck Norris can divide by zero.
[www.chucknorrisfacts.com/page2.html, as of 2009-02-22]

If you have five dollars and Chuck Norris has five dollars, Chuck Norris has more money than you.
[www.chucknorrisfacts.com, as of 2009-02-22]

The square-root of -1 is not imaginary. It is just hiding from Chuck Norris.
[Ben, 2009-02-22]

The shortest distance between two points is Chuck Norris.
[original, 2009-02-22]

The square root of 2 is rational number for Chuck Norris.
[org.]

Chuck Norris can square the circle, double the cube and trisect an angle using only his fingers for a compass and his arm for a straight edge.
[org.]

Flummoxed by his true-false final exam, a student decides to toss a coin up in the air. Heads means true; tails, false. Thirty minutes later, he is done, well before the rest of the class. But then the student startsd flipping the coin again. And soon he’s swearing and sweating over each question.

“What’s wrong?” asks the concern teacher.

“I’m rechecking my answers,” says the student.

[Comic Wendell Potter, Laugh!:), Reader Digest, March 2009, p. 81]

Uri’s Comment: It is interesting to note that the student can change any answer that is not confirmed without affecting the probable grade of the test. Of course, for this to be true, the number of questions should be as large as possible. Considering that (a) it took the students 30 min. to finish the test and (b) it takes under 6 seconds to toss a coin and jot down the result, the test could have consisted of 150-300 questions (no need to spend time on reading each question). This test consists of a sufficient number of questions for probability to determine the overall grade.

Having the modest goal to create artificial life, Theo Jansen not only invented a new wheel, a better wheel, and employed math, geometry and science to new extremes but also successfully accomplished his goal.

With the right mathematical tools, starting with numerical data and using visual representation, Hans Rosling, a Swedish statistician, present an alternative view of the geopolitical world.

Starting at 11:30 (min:sec) of the video clip, listen to the sound of the juggling pins as they hit the jugglers’ palms – the rhythm is an auditory pattern. Freeze frame the video and see their trajectories. These are visual geometric patterns. The two types of patterns coincide.

The words listed below have something in common. What is it? For an extra reward, i.e., more satisfaction, can you arrange them in the proper sequence according to this common trait of theirs? And for even more satisfaction, if you are up for the challenge, add the last word of the sequence.

A hint, one word in the list does not share the common attribute. However, in one important respect it does belong to the sequence and therefore serves as a hint to the solution.

Is it always true that if you have a good thing, then having more of it is better and, conversely, if you got something bad having more of it is worse? Case in point, consider the following situation (usually told as a joke):
“What is worse than finding a worm in the apple you are eating?”
“I don’t know… Two worms.”
“No. Half a worm!”

Thousands of people enjoy doing and watching the wave. The sense of comradeship and sharing is most powerful. But the the beautiful pattern created by the synchronized crowd is magnificent.

Thousands of people enjoy doing and watching the wave. The sense of comradeship and sharing is most powerful. But the the beautiful pattern created by the synchronized crowd is magnificent. You can hear the excitement in the voice of the woman.
[USC vs. Arizona State Football Game]

I am always amazed at the ingenuity of the human mind. I’ve always been interested in and even fascinated by knots and tying. I’ve known several ways of tying shoelaces and did not give it much thought. I considered it so simple, once it was tied, the shoelace knot is one of the most basic knots. nothing to it.

Wrong!

Several years ago, when my son was in first grade I was awed by one of his classmates, a second grader, when I saw how she tied her shoelaces in a single, fluid motion. I asked her to repeat it and she did but her fingers always moved too fast for my eyes to catch the details of her action. The result, however, was the familiar knot. She told me that this is the only way she knew to tie her laces.

Then I came across this video and I learned how to tie my shoelaces in the same way.

It’s not difficult and you can do it too and fascinate your friends.

I have found one problem with the book, a publishing problem, and I wish that Hudson Street Press, the publisher, will fix it for the next edition. The problem is this:

If a girl or someone who loves her is shopping at Borders or Barnes & Noble store, they would probably browse the Young Adult section, perhaps even the Young Adult Nonfiction shelves. Unfortunately Math Doesn’t Suck can be found only in the math section of brick and mortar or online bookstores.

I suspect that the culprit is the classification of the book as MathematicsStudy and Teaching, Middle School (see the back side of the title page.) Before its next edition, paperback Im certain it will have one or otherwise comes out, Hudson Street Press should also list this title under something like Young Adults, Girls Life. I am suggesting this not because the book deserves this classification, which it does, but more importantly, girls and anyone, who cares for them, should be able to come across it without having to mistakenly wonder into the math section of the store.

The language teacher: “In most languages a double negative means the positive but in no language a double positive means the negative.”

A student at the back of the classroom sneers: “Yeah, yeah!”

(According to John Allen Paulos this joke is based on a “true story” that took place during “a talk on linguistic” given by a “well-known philosopher”, which he did not name. The person who responded with the double-positive was “another well-known philosopher.” [Mathematics and Humor, p. 43.])

On Sept. 9, 2007, Asafa Powell broke his own 100-meter sprint/dash world record, his new record is now 9.74 sec. This race and his record can be a source for interesting calculations:

1. how many steps it takes the runners to cover 100 m?

2. what is the average step size?

3. What is their speed in terms of mph?

4. How much time during the race they spend in the air (as oppose to touching the ground)?

This can be evaluated/estimated by viewing the video frame by frame.

I believe it is more than half the time.

Look at it another way, with respect to distance, not time:
Most of the 100-meter distance he covers while he is airborne. If so, in a sense, with respect to distance, he is flying. But this is a misrepresentation because he must touch the ground every step in order to propel his airborne self for the next segment of his flight.

5. Assuming that Asafa Powell’s weight is still 88 kg (per Wikipedia’s older article), then:

It is common among friends and relatives of professionals to expect a favorable treatment, that is, a discount or a freebie, when they need the service or product of their professional friend. And it is almost just as common practice for the professional to oblige with such an expectation. For example, if you have a friend who is a plumber, I dare presume that, when your toilet is plugged and you urgently need a plumber, you might call your plumber friend, ask his assistance and expect him to give you a discount or perhaps even a freebie. You may then reciprocate buying him a dinner or a bottle of wine but the value of this thank-you gift is much lower than the value of the service.

Or, say, your friend is an author who just published a new book. You probably expect her to give you a free copy of the book, perhaps even an autographed one with a personal dedication. My question is this:

In mutual relationship, why it is the pro who has to favor you? Why dont you favor the pro?

Consider the example of your author friend. Why should she give you a free copy of her book? Why shouldnt you buy her book and pay double its price?

OK, I know, the bookseller cant take a payment larger than what they sell it for but you get the idea. Beside, we can figure out a workaround this formal limitation. For if you truly like your friend and want to (a) encourage her writing and/or (b) encourage her publisher to publish more of her books and/or publish more books of this kind, then you can send the extra payment with an explanation to either the publisher or your friend the author. Or at least, buy the hardbound book at a full-price retailer, not a paperback at discounter, and then, when the paperback comes out, buy it too.
Where is the math here?

Think of positive and negative numbers and especially think of the duality between the positives and negatives. In this case, why the positive should be a discount for you and the financial negative to your friend and not the other way around?

This is a clear example how positive and negative numbers are often set by the relevant context. For example, if I owe you money, then, as far as I am concerned, my debt to you has a negative value while, from your perspective the debt has a positive value. Similarly, for pilots going up is a positive experience and ascending is indicated by positive numbers and descending by negative numbers. On the other hand, for a scuba diver going into the ocean depth is a most positive experience, so for her descending is measured by positive numbers, which also indicate the increase in pressure, while ascending is measured by negative numbers.

When I talk to students, teachers and others about negative and positive numbers, I like to say: There is nothing negative about the negative numbers.

I will start my collection of math humor with Abbott & Costello. For Abbott and Costello loved to perform funny mathematical routines. Some they performed in different settings. I once heard that they had a mathematician among their writers. Many of their mathematical skits are quite famous. I think that their most famous routine, Whos On First’ is funny because of its mathematical point of view (I will explain it in that post.)

Can you figure out why these skits are so funny? What is wrong with the math and how to fix it?

The mathematical connection of this famous routine is not obvious. But some important math concepts are at the root of this funny skit.

After you stop laughing and, if you are like me, wipe the tears so you can see straight, you may take a minute to think about why this is so funny. Clearly it is the use of ordinary words as proper names. But “who” and “what” are not just ordinary words. These are pronouns.

Considering the history of human languages, nouns, proper names and pronouns predate numbers, constants and variables by thousands of years. More importantly natural languages, like English and Chinese are much older than formal languages like the semantic aspect of mathematics. This is a very important point to keep in mind. For math, as a language, abhors ambiguities. Math cannot tolerate confusing numbers and variables. In mathematical terms proper nouns are numbers or constants and pronouns are are variables and in “Who’s On First?” Abbott and Costello do just that — they confuse numbers or constants with variables.

I include “Who’s On First?” in my math-humor collection because what makes it funny is the absurd exchange. And these absurds are rooted in ambiguities that we may tolerate in most normal communications. For a few moments we are made to see, if not to understand, the mathematical viewpoint of such ambiguities. This is an excellent illustration of the connection of strict mathematical concepts to ordinary language. If we remember this fact, we can often make those formal mathematical ideas much easier to understand.

I have written a procedure for dynamic subtraction, in which borrowing is replaced by dynamic addition and the subtraction that has to be done is much simpler: it is done within each place-value column, in any order; that is, subtracting the single-digit numbers in each column is completely independent of anything you do in any of the other columns. You can read more about it iin the following sites:

Math is perfectly precise. It has to be. Math cannot depend on our ability to draw a straight line, calculate some result or on whether or not we can perform any other mathematical task. Mathematicians have recognized that, no matter how hard anyone tries, it is impossible to achieve, let alone maintain, the precision level math requires. So the mathematical system, which generations of mathematicians developed, accepts our imperfect capabilities and overcomes the drawbacks by maintaining a simple principle. We must be as precise as we can under the given circumstances and do our best to avoid ambiguities. Once we do that, our imprecise mathematical communications can represent perfectly precise mathematical thoughts.

Math is the study of patterns and relationships.
Math explores the world, real and imaginary, by searching for, discovering and studying patterns and relationships. To do so, math employs logic, the art of reasoning. In turns, science, the study of figuring things out, which in turns employs math.