June 12, 2009 by Uri.

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]

Posted in Jokes, Reader's Digest, Math Humor, Fractions | No Comments »

February 22, 2009 by Uri.

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.]

Posted in Math Education, Math Humor, Math | 1 Comment »

February 21, 2009 by Uri.

clipped from www.youtube.com Subtraction Without Borrowing by MathVentures [Video Prototype 01]

Posted in Math | No Comments »

February 12, 2009 by Uri.

clipped from www.youtube.com Show Off - The Drowsy Chaperone - Tony Awards

Posted in Math | No Comments »

February 9, 2009 by Uri.

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.

Posted in Probability, Math Humor | No Comments »

March 16, 2008 by Uri.

“To be or not to be,” that is the answer.

What is the question?

Solution

Posted in Math Humor, Math | No Comments »

March 15, 2008 by Uri.

Posted in Wind Energy, Machines, Energy, Physics, TED, Wind Power, Physics Education, Science, Math, Patterns, Math Books, Science Education, Geometry | No Comments »

March 15, 2008 by Uri.

Posted in World development, Visualization, Demography, World Economy, TED, Time, Math Education, Science Education, Math | No Comments »

March 15, 2008 by Uri.

Posted in Physics Education, Math Video, Science Education, Math Teaching, Math Education, Math Learning, Math | No Comments »

March 15, 2008 by Uri.

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.

Posted in Visualization, Visual Patterns, Auditory Patterns, TED, Physics Education, Patterns, Math Learning, Geometry | 1 Comment »

January 30, 2008 by Uri.

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.

The given words are:

Reflection, Cheers, Thousand, Alpha, Scotch, American, Steady, Father, Fourth, Winner, Inn

Solution

Posted in Brain-teaser | No Comments »

December 21, 2007 by Uri.

clipped from www.youtube.com UCLA Marching Band Strike Up the Band For UCLA

Posted in Math | No Comments »

December 21, 2007 by Uri.

clipped from www.youtube.com 2006 UCLA Drumline

Posted in Math | No Comments »

December 21, 2007 by Uri.

clipped from www.youtube.com Alabama A-Day Game 2007: Crowd Doing The Wave

Posted in Math | No Comments »

December 21, 2007 by Uri.

clipped from www.youtube.com USC vs. Arizona State - Football Game Wave!

Posted in Math | No Comments »

October 17, 2007 by Uri.

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.])

Posted in Math Humor | No Comments »

September 10, 2007 by Uri.

Asafa Powell Bonita Jamaica Fastest

Originally uploaded by Bonita Jamaica

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:

5.1. What is his acceleration?

5.2. How much force he spent?

5.3. How much energy?

Posted in Uncategorized | No Comments »

September 10, 2007 by Uri.

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 don’t you favor the pro?

Consider the example of your author friend. Why should she give you a free copy of her book? Why shouldn’t you buy her book and pay double its price?

OK, I know, the bookseller can’t 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.

Posted in Negatives and Positives, Math Reasoning | No Comments »

July 23, 2007 by Uri.

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, “Who’s 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?

Posted in Abbott and Costello, Math Humor | No Comments »

July 23, 2007 by Uri.

clipped from www.youtube.com

Posted in Uncategorized | No Comments »

July 23, 2007 by Uri.

clipped from www.youtube.com

Posted in Uncategorized | No Comments »

July 23, 2007 by Uri.

clipped from www.youtube.com

Posted in Uncategorized | No Comments »

July 23, 2007 by Uri.

clipped from www.youtube.com

Posted in Uncategorized | No Comments »

July 22, 2007 by Uri.

clipped from www.youtube.com

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.

Posted in Uncategorized | No Comments »

May 27, 2007 by Uri.

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:

• MathVetures

1. Simplified Procedure
2. Original (light) Procedure
3. PDF download of this original version
4. Detailed Explanation (download a PDF file)

• Wikipedia

1. Subtraction Without Borrowing (my article)

Posted in Subtraction, Addition, Arithmatic | No Comments »

May 25, 2007 by Uri.

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.

Posted in Ambiguity, Math, Precision | No Comments »

May 23, 2007 by Uri.

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.

Posted in Patterns, Science, Logic, Math | No Comments »