Friday Word Puzzle

Sometimes, a small word is contained in a longer word. For example, you can see the three-letter word rid tucked nicely inside Friday in the title for this post, and zip can be found in the middle of marzipan.

Some folks have told me that the following word-in-a-word is particularly appropriate for this blog…


…since my puns put the UGH in LAUGHTER.

Words within words are the basis of today’s puzzle.

Complete each of the nine words below by placing a three-letter word in the blank. The three-letter words that you use all belong to the same category. But there is a tenth three-letter word from the same category that is not used below. What is the category, and what is the missing word?

  1. OB _ _ _ D
  2. C _ _ _ PY
  3. M _ _ _ OT
  4. PH _ _ _ M
  5. H _ _ _ SE
  6. VE _ _ _ D
  7. CA _ _ _ OU
  8. EL _ _ _ SE
  9. LE _ _ _ E

When I started to create this puzzle, I was hoping to give you a similar list in which a short math word was found in a longer word. I found several, but they seem pretty darn hard, and the missing words aren’t always obviously mathy. But for fun, you can try your hand at these, too…

  1. D _ _ _ Y
  2. AS _ _  _ E
  3. SE _ _ _ H
  4. BU _ _ _ _ SS
  5. EL _ _ _ _ TH
  6. C _ _ _ _ RA
  7. RU _ _ _ _ NT
  8. SH _ _ _ _ BLE
  9. BRA _ _ _ _ ILD
  10. HU _ _ _ _ D
  11. PR _ _ _ _ _ IFY
  12. RE _ _ _ _ NT
  13. WA _ _ _ _ ELON
  14. DE _ _ _ _ OR
  15. HO _ _ _ _ SS
  16. H _ _ _ _ HOG
  17. IM _ _ _ _ ST



  1. OB eye D
  2. C hip PY
  3. M arm OT
  4. PH leg M
  5. H ear SE
  6. VE toe D
  7. CA rib OU
  8. EL lip SE
  9. LE gum E

The three-letter words are all parts of the body. The tenth word in that category is jaw, which never appears in the interior of a longer word (only at the beginning or end, such as jawbone or lockjaw).

  1. D add Y
  2. AS sum E
  3. SE arc H
  4. BU sine SS
  5. EL even TH
  6. C hole RA
  7. RU dime NT
  8. SH area BLE
  9. BRA inch ILD
  10. HU more D
  11. PR equal IFY
  12. RE side NT
  13. WA term ELON
  14. DE mean OR
  15. HO line SS
  16. H edge HOG
  17. IM mode ST

June 23, 2017 at 5:30 am Leave a comment

The Amazing National Flag of Nepal

The National Flag of Nepal is unique.

Nepal Flag

Here are several trivia questions about the Nepalese flag:

  1. It is the only non-quadrilateral national flag in the world. What is its shape?
  2. It is one of only three national flags where the height is not less than the length. What are the other two?
  3. What is the sum of the three acute interior angles within the flag?

Question 3 may be difficult to answer without knowing more about the exact dimensions of the flag. For help with that, we turn to the Constitution of Nepal, promulgated 20 September 2015, which contains the following geometric description for the construction of the flag:

The method of making the National Flag of Nepal

  1. Method of making the shape inside the border
    1. On the lower portion of a crimson cloth draw a line AB of the required length from left to right.
    2. From A draw a line AC perpendicular to AB making AC equal to AB plus one third AB. From AC mark off D making the line AD equal to line AB. Join B and D.
    3. From BD mark off E making BE equal to AB.
    4. Touching E draw a line FG, starting from the point F on line AC, parallel to AB to the right hand-side. Mark off FG equal to AB.
    5. Join C and G.

The traditionalist in me wishes that “line segment” were used instead of “line,” or that the overline were used to indicate those segments, and that a few more commas were inserted to make it more readable. Consequently, the math editor in me feels compelled to rewrite the directions as follows:

Nepal Flag Method Math

But the American in me — given how many times someone in the United States has tried to legislate the value of π — well, I’m just excited to see accurate mathematics within a government document.

The description continues for another 19 exhilarating steps, explaining how to construct a crescent moon in the top triangle, a twelve-pointed sun in the bottom triangle, and a border around the shape described above. Those steps are omitted here — because you surely get the gist from what’s above — but the following “explanation” that appears below the method is worthy of examination:

The lines HI, RS, FE, ED, JG, OQ, JK and UV are imaginary. Similarly, the external and internal circles of the sun and the other arcs except the crescent moon are also imaginary. These are not shown on the flag.

The entirety of this construction, as any classical geometrician would hope, can be completed with compass and straightedge. I cheated a bit and used Geometer’s SketchPad, with this being the resultant mess:

Nepal Flag Construction

Geometer’s SketchPad Construction of Nepalese Flag

The rough part was placing C so that AC = AB + 1/3 AB. Geometer’s SketchPad could have easily measured AB, calculated 4/3 of its length, and then constructed a “circle by center and radius,” but that felt like cheating. Instead, I…

  • located Q, which is halfway between A and D;
  • constructed circle A with radius AQ = AP;
  • constructed circle P with radius PD;
  • constructed circle D1 with radius DA;
  • located the intersections of circle P and circle D1 at points X and Y;
  • constructed a line through X and Y;
  • located R, which is 1/3 of the way from D to A;
  • constructed circle D2 with radius DR; and,
  • located C, so that CD = 1/3 AB.

Now, you could use that information to determine CF and FG, and then use the arctan function to calculate the measures of the two acute angles in the upper pennon. If you were so inclined, you’d find that their measures are 32.06° and 57.94°, respectively.

But the question above asked for the sum of the three angle measures. Without any work at all, it’s clear that the sum of those two angles must be 90°, since the construction described above implies that ΔCFG is a right triangle.

And because AB = AD by construction, then ΔDAB is an isosceles right triangle, and the measure of the third acute angle must be 45°.

And that brings us to a good point for revealing the answers to the three questions from above.

  1. Pentagon
  2. The flags of Switzerland and Vatican City are square, so the height and width are equal.
  3. 135°

If you’re looking for more flag-related fun, check out the MJ4MF post from Flag Day 2016 about converting each flag to a pie graph.

June 7, 2017 at 9:38 pm Leave a comment

A Ton of Money (or Maybe More)

One of my favorite resources from Illuminations is Too Big or Too Small, a collection of three classroom activities that develop number sense, one of which is the following problem:

Just as you decide to go to bed one night, the phone rings and a friend offers you a chance to be a millionaire. He tells you he won $2 million in a contest. The money was sent to him in two suitcases, each containing $1 million in one-dollar bills. He will give you one suitcase of money if your mom or dad will drive him to the airport to pick it up. Could your friend be telling you the truth? Can he make you a millionaire?

This problem is from the book Developing Number Sense in the Middle Grades by Barbara Reys and Rita Barger, published by NCTM in 1991. So it’s not new, but it’s still good.

Million Dollar Bill

© NCTM 2017

My first attempt to use this problem with students was dreadful (details below), but I’ve used this problem successfully many times since. Yet something about it always bothered me. I’m not opposed to fictitious scenarios if they get students interested. But this scenario, in which a friend claims to win $2,000,000 and needs a ride to the airport, seems too contrived and not adventurous enough. Luckily, I recently had food poisoning and spent an entire Saturday on the couch watching bad movies. While watching Rush Hour (1998), I found a scenario that I liked a whole lot better…

In the clip, the kidnapper asks for the following:

  • $20 million in $50’s
  • $20 million in $20’s
  • $10 million in $10’s

Now the questions of “How much would that weigh? How big a case would you need to carry all of it?” seem a little more meaningful.

I’ll channel my inner Andrew Stadel here. For both the weight and volume:

  • Give an estimate that you know is too low.
  • Give an estimate that you know is too high.

Now, do the calculations, and see how close your intuition was.

When I first used this task with students, I was anticipating a great discussion about how to estimate the weight and volume of the money. I suspected that some students might estimate that you could fit 5 or 6 bills on a sheet of paper, there are 500 sheets of paper in a ream, a ream weighs about 5 pounds, yada, yada, yada. Instead, one student raised his hand and said:

A dollar bill weighs exactly 1 gram.

I asked how he knew that. “Do you collect money? Are you a numismatist?”

No. That’s how drug dealers measure cocaine. They put a dollar bill on one side of a scale, and they put the cocaine on the other.

“Oh,” I said.

Some days, your students learn something from you. And some days, you learn something from them.

After you estimate the weight and volume, check your answer by clicking over to

If you use this video clip and activity in a classroom with students, I’d love to hear how it goes. Please post about your experience in the comments.

June 5, 2017 at 6:02 am Leave a comment

Book Review: Flightmares by Robert D. Reed

FlightmaresBob Reed is likely one of the nicest guys you’ll ever meet. He’s certainly one of the nicest guys in the publishing industry. And he is absolutely, positively the nicest guy to have published Math Jokes 4 Mathy Folks.

Bob has now written his own book of jokes, Flightmares: Sky-High Humor. Chock full of zingers about pilots, flight attendants, mechanics, travel, and aerodynamics, Flightmares does for flying what Jaws did for swimming.

The following are just a few of the gems you’ll find inside:

Flying is the second greatest thrill known to man… landing is the first!

“Why is the mistletoe hanging over the luggage counter?” asked the airline passenger, amid the holiday rush.
The clerk replied, “It’s so you can kiss your luggage good-bye!”

I think my favorite jokes are the ones that could appear in a math joke book, with a little revision. Like this one, which I’ve heard in reference to a mathematician instead of a pilot:

What’s the difference between God and an airline pilot?
God doesn’t think He’s a pilot.

Or this one, if you replace flight attendants on an airplane with a math teacher in a geometry class:

What kind of chocolate should flight attendants hand out on airplanes?
Plane chocolate, of course.

And there’s even one that could be used in a math joke book directly:

Gunter’s Second Law of Air Travel: The strength of the turbulence is directly proportional to the temperature of the coffee.

What more can I tell you about Flightmares? Just like passengers on a jet that’s lost all four engines, it’s a scream! Well worth the price for some light summer reading.

To learn more about Flightmares, or for quantity discounts, visit Robert D. Reed Publishers. To purchase individual copies, visit Amazon.

May 26, 2017 at 5:56 am Leave a comment

Russell, Robertson, and Ratios

In the NBA, a triple-double happens when a player has a double-digit total in three of the five categories (points, assists, rebounds, steals, and blocks) in a game. Triple-doubles are very rare; on average, one has been recorded only once every 27 games since 2003. So far this season, there have been 111 triple-doubles throughout the entire NBA — and Russell Westbrook has 41 of them.

Russell Westbrook

Russell Westbrook

In 1961-62, Oscar Robertson set a record that Westbrook is about to break. That year, Robertson recorded 41 triple-doubles in 80 games. Westbrook recorded his 41st triple-double of the current season in just 78 games. When two fractions have the same numerator, the one with the smaller denominator is larger. Consequently, 41/78 > 41/80, so Westbrook’s accomplishment exceeds Robertson.

Oscar Robertson

Oscar Robertson

But ratios can be used to make the point even more dramatically. In the early 1960’s, pro basketball games were played at a faster pace than they are today. In 1961‑62, the average game featured 126.2 possessions, meaning that Robertson typically had more than 60 tries to grab a rebound, make an assist, or score some points. By comparison, there have been an average of just 96.4 possessions per game during the current NBA season, meaning that Westbrook generally has fewer than 50 attempts per game to improve his stat line. So another ratio — the comparison of points, rebounds, and assists to number of possessions — also leans in Westbrook’s favor.

Who knew that either of these guys were such fans of math?

At Discovery Education, we’ve been having a lot of fun writing basketball problems based on real NBA data. Check out a few problems at, and get a glimpse of the NBA Analysis Tool within Math TechbookTM by signing up for a free 60-day trial at

DE and NBA Math


April 9, 2017 at 5:43 pm Leave a comment

Big Brother Knows My Sons Are Smarter Than I Am

CWGYHEL QUizWhile pointing and clicking, I stumbled upon an online quiz, Can We Guess Your Education Level? Intrigued, I tolerated the 70‑question multiple-choice quiz to see if they could make an accurate prediction. Sure enough, they correctly declared, “It looks like you’re a master with that Master’s Degree.”

How did they know?

The optimist in me thinks they use some incredible adaptive engine to figure out exactly what I know and what I don’t, and then they use that information with a correlation of what people at various educational levels know. Sounds plausible, right?

But the pessimist in me was pretty sure they just mined info from my LinkedIn and Facebook profiles, and they likely knew the answer before I responded to a single question.

So, I tested my theory. I took the quiz a second time and deliberately missed a bunch of questions. When I finished, I scored only 21%, and they told me, “It appears that you completed high school, and then graduated from the School of Life.”

Okay, so it is at least based on percent correct. I’m still dubious that it’s rigorous, but at least it isn’t digging through my personal information just to dupe me.

For fun, my 9‑year old son said that he’d like to take the test. And this is when I knew it was complete bullshit — because he scored higher than I did:

PhD Result

Hold on a second. You’re telling me that I spent five glorious years at the Pennsylvania State University earning my undergraduate degree, and then I spent five magnificent years at the University of Maryland earning my master’s degree, and yet my son — who hasn’t spent even five years total in the educational system — was able to outperform me on an academic quiz?

“Hello, is this Penn State? I’d like my money back.”

What really got me, though, is that the math on this quiz — just like every other online quiz, multidisciplinary test, and academic competition — was paltry.

Speed Question

There were seven math-related questions on the test, none of which rose above the level of “basic,” and some were even lower than that. But don’t take my word for it; decide for yourself…

  1. Speed is defined as…
  2. What is the name of the result when you add four numbers and then divide the sum by 4?
  3. What is the definition of binary?
  4. How many events are in a decathlon?
  5. What is the value of the Roman numeral IX?
  6. Who wrote The Elements, and what was it about?
  7. The year 1707 is part of which century?

Can we all agree that these are rather easy math questions? It makes me wonder if our discipline is just so abstract or elusive that even the most basic of questions is perceived as difficult by a large portion of the population. If so, what accounts for this perception?

Your thoughts are most welcome.

March 29, 2017 at 4:27 pm Leave a comment

More or Less

“That’s Qatar. Its capital is Doha,” I said as we were talking about world capitals and looking at a map of the Middle East. “It’s a very small country.”

“Doesn’t look much smaller than Djibouti,” Alex replied.

And it’s true. On the map, they don’t look much different in size…


Which led me to wonder, which is larger?

And that one little question led to the creation of a game we now call More or Less, in which one person names two items, and the other person needs to identify which of the two is larger. It’s a great game for passing time on a car trip or during a long walk.

Here are some of our favorites:

Category Option A Option B
Land Area Qatar Djibouti
Percent of U.S. Flag Red White
Distance from St. John’s, NL Vancouver, BC Rome, Italy
Weight $10 in Quarters $10 in Dimes
Population New York City London
Calories Big Mac Whopper
Equatorial Radius Neptune Uranus
Length Distance from North to South Pole Great Wall of China
Official Capacity Rungrado May First Stadium, North Korea Michigan Stadium (“The Big House”)
Caffeine (per 12 fl. oz.) Coca-Cola Pepsi-Cola
Net Worth Jeff Bezos Warren Buffett
Loudness Squeeze Toy Vacuum Cleaner
Stores Worldwide Dunkin Donuts Starbucks
Number by All Teams in a Season Home Runs in MLB Goals in NHL
Top Speed Slug Snail
Heart Beats per Minute Pig Human
Estimated IQ Newton Leibniz
Number of Factors 144 192
Value 316 225

You should definitely try to figure out whether Option A or B is larger in each row above, before you look at the answers below.

And if you can answer at least 15 of these correctly, you’re more or less a genius!


  • Maps can be deceiving. Although they look similar in size, the area of Djibouti is more than double that of Qatar. Djibouti is 23,200 km2, Qatar only 11,586 km2.
  • The U.S. flag is about 41.5% red, 40.9% white.
  • Vancouver is 5,117 km from St. John’s, and Rome is only 5,050 km. (Canada is a big country!)
  • A dime weighs 2.268 g, a quarter weighs 5.670 g. So 100 dimes and 40 quarters will both weigh 226.8 g.
  • London has 8.7 million people. New York has just slightly fewer with 8.6 million.
  • A Whopper (no cheese) has 680 calories, whereas a Big Mac (with its two patties, a slice of cheese, and an extra bun in the middle) has only 540 calories. Go figure.
  • Uranus is larger with a radius of 25,500 km; the radius of Neptune is 24,700 km.
  • Traveling from the North pole to the South pole would be circumnavigating half the Earth, which is about 12,430 miles. But the Great Wall of China is estimated to be 13,170 miles.
  • Rungrado holds 114,000, whereas The Big House only holds just under 108,000.
  • Pepsi has 58 mg of caffeine, Coke only 54 mg.
  • Jeff Bezos is worth $70 billion, Warren Buffett is worth $65 billion. They’re both ridiculously rich, but Bezos was more efficient in acquiring his wealth.
  • A vacuum cleaner will reach 75 dB, which is “slightly annoying,” whereas a squeeze toy can reach 90 dB. A vacuum cleaner seems louder and more annoying because the sound persists, whereas most squeeze toys make a noise once, then stop.
  • In 2016, there were 25,085 Starbucks but only 12,258 Dunkin’ Donuts, according to Statista.
  • There were 6,672 goals scored in the NHL during the 2015-16 season, but just 5,610 home runs hit in the MLB in 2016. There are more than 6,000 hockey goals scored every year, but only two seasons in the past decade have seen more than 5,000 home runs.
  • A fast slug can move 0.2 mph, but the poor snail — with that heavy shell on its back — can only muster about 0.02 mph.
  • An average human’s heart beats about 60 times per minute; an average pig’s heart, about 70.
  • According to The Early Mental Traits of Three Hundred Geniuses by Catharine M. Cox, Leibniz was 183, Newton 168. (Sorry, Isaac!)
  • The number 144 has 15 factors, the number 192 has only 14.
  • 316 – 225 = 9,492,289.

March 23, 2017 at 2:40 am 2 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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