## Posts tagged ‘math’

### Happy as L!

On Wednesday, I’ll complete my 50th trip around the Sun. To celebrate, my friend Kris sent me a card with a wonderful Roman reminder of my age:

Thanks, Kris!

Here are two relatively easy math problems associated with my birthday:

- On Wednesday, how many days old will I be?
- What are the four positive integer factors of the answer you got to Question 1? (Hint: One of the factors is the number of
**weeks**old that I’ll be.)

I recently wrote a book called One Hundred Problems Involving the Number 100. To celebrate my 50th birthday, here are ten problems involving the number 50:

- There are 50 puppies to be adopted at a shelter, and 98% of them are hounds. How many hounds must be adopted so that 90% of the remaining puppies are hounds?
- Let A = 1, B = 2, …, Z = 26. Find two common English words for which the product of the letters is 50.
- What’s the least possible product of two prime numbers with a sum of 50?
- While finding the sum of the numbers 1‑10, I got distracted and omitted some numbers. The sum of the remaining numbers was 50. How many different sets of numbers could I have omitted?
- The square numbers are 1, 4, 9, 16, …, and the non-square numbers are 2, 3, 5, 6, 7, 8, 10, 11, and so on. What is the 50th non-square number?
- Choose three numbers so that one number is selected in each row and each column. What’s the sum of the three numbers?

- A two-player game is played on this number rack with five rows of 10 beads. One player chooses to be Odd, the other Even. The players take turns. On each turn, a player may slide one, two, or three beads from the middle to the side of the rack. Beads moved to the side cannot be moved again. When all beads have been moved, the Odd player earns one point for each row with an odd number of beads on each side, and the Even player earns one point for each row with an even number of beads on each side. The player with the most points wins. What is the optimal strategy, and who should win?
- How many people must be present to have a probability of 50% that two of them will share a birthday?
- Insert only addition and subtraction symbols to make the following equation true:

9 8 7 6 5 4 3 2 1 = 50

- What’s the area of the square? (Inspiration from Catriona Agg, both for the puzzle and for the reduction in words.)

Answers will be posted on my birthday — St. Patrick’s Day! Stop back on Wednesday!

### Change the Vowel

The following puzzle contains a clue within each clue. The answer, of course, fits the clue, but each answer is also one of the words within the clue with its vowel sound changed. For instance, the clue “the distance from the top of your hat to the sole of your shoes” contains the word *hat*, and if you change the vowel sound from a short *a* to a long *i*, you get *height*, which fits the description.

As always, there’s a catch. Every answer to the clues below is a mathy word.

- The number of permutations of three different colored socks.

- This value is the same for 3 + 1 and 2 + 2.
- Do this with two odd numbers and you’ll get an even number.
- Three hours before noon.
- You may fail to correctly expand (
*a*+*b*)(*c*+*d*) if you don’t remember this mnemonic. - One represents this fractional portion of toes on the hoof of a deer.
- The last element of a data set arranged in descending order.
- The measure of central tendency made from the most common data points.
- The number of contestants ahead of third place if there’s a tie for first place.
- If the leader is forced to drop out of a race, the runner-up takes over this place.
- The square root is needed to calculate the length of the hypotenuse in this type of triangle.
- The graph of the declination of the Sun during a year can be approximated by this type of curve.

Answers

- six

- sum
- add
- nine
- FOIL
- half
- least
- mode
- two
- first
- right
- sine

### 100 Problems for the 100th Day of School

In May 2020, I delivered a webinar titled *One-Hundred Problems Involving the Number 100*. Every problem included a problem that somehow used the number 100, maybe as the number of terms in a sequence, the length of a hypotenuse in inches, or the number of digits written on a whiteboard. At the end of the webinar, NCTM President Trena Wilkerson challenged me to create a collection of 100 problems for which the answer is always 100.

So, I did.

My process was simple. I just wrote problem after problem with little concern for topic or grade level. Some of the problems were good; others were not. Some of the problems were difficult; others were easy. Some of the problems required knowledge of esoteric math concepts; others required nothing more than the ability to add and subtract. But I wrote 100 problems, then I reviewed them and deleted those that weren’t good enough. Then I wrote some more, and cut some more, and so forth, until I finally had a collection of 100 problems that were worthy.

And I’m going to share all of them with you in just a minute. But first, a math problem for which the answer is** not** 100.

As I said, I wrote the problems as they came to me, not necessarily in the order that I’d want to present them. But to keep track of things, I numbered the problems 1‑100. Since they were in the wrong order, I had to rearrange them, meaning that Problem 92 in the draft version eventually became Problem 1 in the final collection; Problem 37 became Problem 2; Problem 1 became Problem 3; and so on. You get the idea. So, the question…

You have a collection of 100 items numbered 1‑100, but the items are out of order. When you arrange the items in the correct order, how many would you expect to be labeled correctly? (Less generically, how many of my problems had the same problem number in the draft version and the final collection?)

The solution to that problem is more beautiful than I would have initially guessed. Have fun with it.

Without further ado, here is the collection:

**Problems with 100 as the Answer**

My goal was to release these problems in time for the 100th day of school, which most schools celebrate in late January or early February. I hope this collection reaches you in time. And I present the problems one per page, so you can decide which one(s) you’d like to use with your students. If you teach algebra, then perhaps you’ll print and share Problems 46 and 53; if you teach third grade, perhaps Problem 2 will be more appropriate. But the problems cover a wide range of topics and difficulty levels, so feel free to use whichever ones you like. (Be forewarned, though. The answer to **every** problem is 100, so unless your students are absolutely terrible at identifying patterns, you probably won’t want to share every problem with them. At least, not at the same time. I’m sharing this collection in time for the 100th day of school, but feel free to use any problem at any time.)

My favorite problem in the collection? I like Problem 47:

Above the bottom row, each number in a square is the sum of the two numbers below it. What value should replace the question mark?

Feel free to let me know if you or your students have a favorite.

p.s. – Bonus points if you can identify the origin of the 100 in the image at the top of this post.

### My 0.04 Seconds of Fame

In 2017, I attended the International KenKen Championship and filmed the final round, which I posted previously on this blog. But filmmakers Louis Cancel, Chris Flaherty, and Daniel Sullivan were there that day, too, and their cameras were significantly more sophisticated than my Samsung S8. Their footage of the competition, coupled with myriad interviews of competitors, organizers, and the inventor of KenKen himself, Tetsuya Miyamoto, has resulted in a new documentary, * Miyamoto and the Machine*, recently released by

*The New Yorker*. It tells the story of KenKen’s origins and attempts to answer the question, “Can a computer make puzzles as beautiful as those created by humans?”

Many aspects of the film will appeal to kenthusiasts, but my favorite moment occurs at 17:14. Competitor Ellie Grueskin is competing in the finals, and just over Ellie’s left shoulder is a barely visible, occasionally funny, middle-aged math guy holding — wait for it — a Samsung S8!

Yep, that’s me. I’m a star!

You have to ask yourself, what kind of monster would author such a shamelessly self-promotional post and not even provide one KenKen puzzle for the reader to enjoy? Definitely not me, so here you go.

After you solve the puzzle, definitely watch * Miyamoto and the Machine*. It’s 25 minutes well spent.

### Mathy Zoom Backgrounds

Do you seek the admiration of your colleagues or the respect of your students?

Do you wish to create the illusion that you’re funny and cool?

Do you long to be the envy of your virtual social circle?

Unfortunately, you’re reading a math jokes blog, which means there may not be much hope for you. But a possible start may be to download some of the math joke backgrounds below for your next online meeting. I’ve been using them for the past few weeks, and I don’t think it’d be an overstatement to say that I’m now the envy of the internet. I mean, I’ve got a face for radio, but you have to admit that I look pretty fantastic when there’s a math poem above my head and equations on either side of it:

And guess what? You can look that cool, too!

To use any of the images below, simply right click and “Save Image As…,” then install them as virtual backgrounds (Zoom, Google Meet). If you’d like a better look at any of them before deciding if they’re worth valuable memory on your laptop, just click on an image to open it full screen.

### Mathy Portmanteaux

The term *portmanteau* was first used by Humpty Dumpty in Lewis Carroll’s *Through the Looking Glass*:

Well, ‘slithy’ means “lithe and slimy” and ‘mimsy’ is “flimsy and miserable.” You see, it’s like a portmanteau — there are two meanings packed up into one word.

Interestingly, the word *portmanteau* itself is also a blend of two different words: *porter* (to carry) and *manteau* (a cloak).

Portmanteaux are extremely popular in modern-day English, and new word combinations are regularly popping up. Sometimes, perhaps, there are **too many** being coined. In fact, one author refers to these newcomers as *portmonsters*, a portmanteau of, well, *portmanteau* and *monster* that attempts to capture how grotesque some of these beasts are. An abridged list of portmonsters would include *sharknado*, *arachnoquake*, *blizzaster*, *snowpocalypse*, *Brangelina*, *Bennifer*, *Kimye*, *Javanka*, *fantabulous*, and *ridonkulous*.

Portmanteaux seem to proliferate most easily in B-movie titles, weather, and celebrity couples, but the world of math and science is not free from them. Here are a few mathy portmanteaux, presented, of course, as equations.

**ginormous** = *giant* + *enormous*, really big

**guesstimate** = *guess* + *estimate*, a reasonable speculation

**three-peat** = *three* + *repeat*, to win a championship thrice

**clopen set** = *closed* + *open set*, a topological space that is both open and closed

**b****it** = *binary* + *digit*, the smallest unit of measurement used to quantify computer data

**pixel** = *picture* + *element*, a small area on a display screen; many can combine to form an image

**voxel** = *volume* + *pixel*, the 3D analog to pixel

**fortnight** = *fourteen* + *night*, a period of two weeks

**parsec** = *parallax* + *second*, an astronomy unit equal to about 3.26 light years

**alphanumeric** = *alphabetical* + *numeric*, containing both letters and numerals

**sporabola** = *spore* + *parabola*, the trajectory of a basidiospore after it is discharged from a sterigma

**gerrymandering** = *Elbridge Gerry* + *salamander*, to draw districts in such a way as to gain political advantage (In the 1800’s, Governor Elbridge Gerry redrew districts in Massachusetts to his political benefit. One of the redrawn districts looked like a salamander.)

**megamanteau** = *mega* + *portmanteau*, a portmanteau containing more than two words, such as DelMarVa, a peninsula that separates the Chesapeake Bay from the Atlantic Ocean and includes parts of Delaware, Maryland, and Virginia

**meganegabar** = *mega* + *negative* + *bar*, the line used on a check so that someone can’t add “and one million” to increase the amount

(By the way, when Rutgers University invited *Jersey Shore* cast member Snooki Polizzi to speak to students on campus in 2011, they paid her $32,000, which is $2,000 more than they paid Nobel and Pulitzer Prize winning author Toni Morrison to deliver a commencement address six weeks later.)

### Getting Back to My Roots

For years, this blog represented the finest mathematical humor that the internet had to offer. That hasn’t been the case so much recently, so it’s time I got back to my roots — of course, for me, those would be cube roots…

I was inspired to craft this post of horrendously bad puns when my sister’s friend shared this photo with me:

And I figured if I have to suffer, you should, too.

How many math grad students does it take to change a light bulb? Just one, but it takes nine years.

What’s the best tool for math class? Multi-pliers!

Think outside the regular quadrilateral.

When asked how good she was at algebra, the student replied, “Very able.”

What’s the difference between the radius and the diameter? The radius.

Are you depressed when you think about how dumb the average person is? Well, I’ve got bad news for you… nearly half the population is even dumber.

How do you make one disappear? Add a

g, then it’sgone.

Writing haiku is

tough, because you have to count.

Writers don’t like math.

Light travels faster than sound. This is why some people appear bright until you hear them speak.

The grad student had trouble getting the pizza box into the recycling can. It was like trying to put a square peg in a round hole.

How is the moon like a dollar? Both have four quarters.

Don’t look now, but there’s a suspicious man over there with graph paper. I think he’s plotting something.

### One-Hundred Problems Involving the Number 100

Although the following joke appears in **Math Jokes 4 Mathy Folks** —

Why was the math book sad?

Because it had so many problems.

— I’ve often contended that it isn’t true. Math books aren’t sad because they have too many *problems*. They’re sad because they have too many *exercises*.

But my forthcoming book isn’t the least bit melancholy, because it contains a multitude of honest-to-goodness, classroom-tested, student-approved, 100% legit math problems — a century of them, in fact, as implied by the title.

**Disclaimer:** The title is a lie. The book actually contains 101 problems. I was so excited, I just couldn’t stop myself when I got to 100. But don’t you worry; there’s no charge for that extra 1%.

As a sample, here are four problems from the book. To experience a fifth problem, register for an **NCTM Author Panel Talk** on Wednesday, October 7, 7:00 p.m. ET, when Marian Small, Roger Day, and I will be discussing rich tasks and sharing samples from each of our new books. The webinar will be moderated by NCTM Board Member Beth Kobett. Hope to see you there!

### Talking Math and Coronavirus With Your Kids #tmwyk

Nothing like a global pandemic to spark a good math conversation.

If you’re a parent from Alabama, Florida, Illinois, Kentucky, Louisiana, Maryland, Michigan, New Mexico, North Carolina, Ohio, Oregon, Pennsylvania, Rhode Island, South Dakota, Virginia, Washington, West Virginia, and Wisconsin — and by the time this post is published, probably many other states — then you’ve got several weeks of quality time with your kids ahead of you. You may be wondering what you can do to fill their time in meaningful and productive ways. Well, my recommendation is to **talk math any time you’re with your kids**, but while COVID-19 is in the news, that suggestion may be more important than ever.

It won’t be long before you tire of questions from your kids about why they have to spend the next two to four weeks at home, about why you won’t let them go to the mall, about why their friends can’t come over, about why they shouldn’t play tag or duck, duck, goose. But don’t get frustrated by their questions. That curiosity is an opportunity to talk about the math of the pandemic while reinforcing the reasons for staying home.

The spread of any disease is dependent on four factors:

- the population of opportunity;
- the number of days an infected person remains contagious;
- the number of people with whom an infected person comes in close contact; and,
- the likelihood of contraction when close contact occurs.

Simulations based on these four factors can be conducted with the **NCTM Pandemics** app (which, unfortunately, requires Flash). The page on which that app resides talks about swine flu, because the app was developed in 2006. But the lessons to be learned from the app are as relevant today — maybe even moreso — as they were 14 years ago.

You can explore on your own, or you can watch the screencast below to see how the spread of coronavirus can be controlled if we all do our part to limit close contact with others.

With your kids, research and discuss appropriate numbers for each factor.

- For display purposes, the app limits the “population of opportunity” to 400. This number falls significantly short of the nearly 8 billion people worldwide who might be infected with coronavirus, but it’s enough to make a point.
- The number of days an infected person remains contagious is unknown, but healthline says that “people who have the virus are most contagious when they’re showing symptoms” and the infection starts with mild symptoms that “gradually get worse over a few days.” It’s reasonable to estimate that an infected person might be contagious for three to five days.
- The number of contacts is
**the only factor**over which we have control. If you go to work or a shopping center, you may have contact with 20 people a day; if your child goes to school, she may interact with 50 other students. But if you follow CDC guidelines, stay home from work or school, and avoid public gatherings, you can reduce the number of contacts to just a handful. - Finally, the chance of contraction is unknown. What is known is that an infected person is likely to transmit COVID-19 to between 2.0 and 2.5 other people if some type of quarantine does not occur. The corresponding chance of contraction would be in the range of 2-4%.

To convince your kids that staying home is a good idea, run the simulation with a large number of contacts. Even if the number of days contagious and chance of contraction are low, **most of the population will become infected if the number of contacts is high**. But then reduce the number of contacts and run the simulation again. **As the number of contacts decreases, so, too, will the percent of the population that gets infected as well as the number of days before the pandemic burns itself out. **

Of note, most of the population will be infected if the days contagious and chance of contraction are both high, regardless of the number of contacts. For instance, if days contagious and chance of contraction are both set to 10, then more than 80% of the population will be infected in the vast majority of simulations, even if the number of contacts is set to 2. However, there are very few diseases for which a person remains contagious for 10 days and the chance of contraction is 10%; and, those numbers are certainly higher than the data would suggest for COVID-19.

### Chuck Norris Math (and Some Science) Jokes

My sons, of course, know that 73 is the Chuck Norris of numbers:

But it hadn’t occurred to me until recently that they had no idea who *Chuck Norris* is. Explaining who he is — that is, trotting out his resume and discussing *Lone Wolf McQuade* and *Walker, Texas Ranger* — is easy enough. But impressing upon them why he’s a bad ass who deserves his own meme? Well, that’s a bit tougher.

But it doesn’t matter. Chuck Norris jokes are just plain funny, even if you have no idea who he is. They’re a genre unto themselves, and the inventor of Chuck Norris jokes deserves as much credit as the inventors of knock knock jokes, one-liners, non-sequiturs, and light bulb jokes.

And I know you’re gonna find this surprising, but of all the Chuck Norris jokes on the internet, my sons most appreciate those involving math. So I present a collection of Chuck Norris math jokes, pulled from various corners of cyberspace, and I hope you enjoy them as much as Alex, Eli, and I do.

Chuck Norris can divide by zero.

Chuck Norris counted to infinity… twice.

The easiest way to determine Chuck Norris’ age is to cut him in half and count the rings.

Using only compass and straightedge, Chuck Norris once trisected an angle and squared a circle simultaneously, one with each hand.

When chuck Norris does division, there are no remainders.

A roundhouse kick from Chuck Norris is faster than the speed of light. This means that if you flip a light switch, you’ll be dead before the light turns on.

Chuck Norris’s body temperature is 98.6 degrees… Celsius.

Chuck Norris can win a game of Connect Four in only three moves.

Chuck Norris can solve a system of equations involving parallel lines.

Chuck Norris can recite the digits of π… *backwards*.

Chuck Norris knows the biggest prime number.

Chuck Norris has every real number tattooed on his forearm.

Chuck Norris doesn’t do mathematics. Chuck Norris *is* mathematics.

Chuck Norris will decide if *P* = *NP*.

If a barber in a village shaves all men who do not shave themselves, then who shaves the barber? Chuck Norris does. Well, sorta. He gives the barber a roundhouse kick and knocks all the hairs from the barber’s face, proving that set theory is both consistent and complete.

Chuck Morris constructed a proof of Fermat’s Last Theorem that would fit within the margin.

If you type 5,318,008 into a calculator and turn it upside down, it’ll spell BOOBIES. If Chuck Norris turns a slide rule upside down, it’ll be so scared that it’ll spell anything Chuck Norris wants it to.

Chuck Norris doesn’t do linear programming; for him, there are never any constraints.

Chuck Norris doesn’t avoid calculation mistakes. Calculation mistakes avoid Chuck Norris.

Chuck Norris can cross a vector with a scalar.

Chuck Norris destroyed the periodic table, because he only recognizes the element of surprise.

Why is 6 afraid of Chuck Norris? Because Chuck Norris 8 9.