Heavy Cookies, Undervalued Coins, and Misconceptions

Simple question to get us started…

Which is worth more?

Quarters and Nickels

And of course the answer is, “The quarters, because 50¢ is more than 20¢,” right? But not to a kindergarten student or a pre-schooler who hasn’t yet learned how much coins are worth. A young student might argue, “Four is more than two.”

Why didn’t the quarter follow the nickel when he rolled himself down the hill?
Because the quarter had more cents.

Recently, I was asked to review an educational video for kindergarten math that had a similar question.

Heavy Cookies

The video stated, “Can you tell the green, yellow, and orange cookies are heavier? That makes sense, doesn’t it? Because there are more of them!”

Uh, no.

This is the same logic that would lead one to claim that the value of four nickels is greater than the value two quarters because there are more nickels. It’s a huge misconception for students to focus on number rather than value. So it’s very frustrating to see this video reinforce that misconception.

For example, if each green, yellow, or orange cookie weighs 3 ounces, but each blue or purple cookie weighs 5 ounces, then the left pile would weigh 6 × 3 = 18 ounces, and the right pile would weigh 4 × 5 = 20 ounces, so the right side would be heavier. (Then again, are there really 6 cookies on the left and 4 on the right, or are some cookies hidden? Hard to tell.)

As far as I’m concerned, the only acceptable answer is that the pile of green, yellow, and orange cookies must be heavier — assuming, of course, that the balance scale isn’t malfunctioning — because the pans are tipped in that direction.

All of this reminds me of the poem “Smart” by Shel Silverstein.

SMART

My dad gave me one dollar bill
‘Cause I’m his smartest son,
And I swapped it for two shiny quarters
‘Cause two is more than one!

And then I took the quarters
And traded them to Lou
For three dimes — I guess he don’t know
That three is more than two!

Just then, along came old blind Bates
And just ’cause he can’t see
He gave me four nickels for my three dimes,
And four is more than three!

And I took the nickels to Hiram Coombs
Down at the seed-feed store,
And the fool gave me five pennies for them,
And five is more than four!

And then I went and showed my dad,
And he got red in the cheeks
And closed his eyes and shook his head–
Too proud of me to speak!

April 30, 2016 at 6:49 am 1 comment

All Systems Go

I noticed the boys having an intense conversation in front of this sign at our local pizza shop:

Flippin Pizza Sign

When I asked what they were doing, they said, “We’re trying to figure out how much one slice and a beer would cost.”

As you read that, there were likely two thoughts that crossed your mind:

  • Why can’t these poor boys look at a pizza menu without perceiving it as a system of equations?
  • Why are eight-year-olds concerned with the price of beer?

The answer to both, of course, is that I’m a terrible father, and both beer and math are prominent in our daily lives.

But you have to admit that it’s pretty cool that my sons recognized, and then solved, the following system:

\begin{array}{rcl}  2p + s & = & 6.00 \\  2p + b & = & 8.00 \\  p + s & = & 3.50 \end{array}

They didn’t use substitution or elimination because they didn’t have to — and, perhaps, because they don’t know either of those methods yet. But mental math was sufficient. If two slices and a soda cost $6.00, and one slice and a soda cost $3.50, then one slice must be 6.00 – 3.50 = $2.50. Consequently, two slices cost $5.00, so a beer must be 8.00 – 5.00 = $3.00. A beer and a slice will set you back $5.50.

I remember once visiting a classroom in Somerville, MA, and the teacher was reviewing the substitution method. My memory is a bit fuzzy, but the problem she solved on the chalkboard was something like this:

Mrs. Butterworth’s math test has 10 questions and is worth 100 points. The test has some true/false questions worth 8 points each and some multiple-choice questions worth 12 points each. How many multiple-choice questions are on the test?

The teacher then used elimination to solve the resulting system:

\begin{array}{rcl}  t + m & = & 15 \\  5t + 10m & = & 100 \end{array}

The math chairperson was standing next to me as I watched. “Why is she doing that?” I asked. “You don’t need elimination. It’s clear there have to be 8 or fewer multiple-choice questions (8 × 12 = 96), so why not just guess-and-check?”

“Because on the MCAS [Massachusetts Comprehensive Assessment System], if they tell you to use elimination but you solve the problem a different way, it’ll be marked wrong.”

So much for CCSS.Math.Practice.MP1. Although most of us would like students to “plan a solution pathway rather than simply jumping into a solution attempt,” apparently students in Massachusetts need to blindly follow algorithms and not think for themselves.

The following is my favorite system of equations problem:

I counted 34 legs after dropping some insects into my spider tank. How many spiders and how many insects?

Why is this my favorite system of equations problem? Because there is a unique solution, even though it results in just one equation with two unknowns. Traditional methods won’t work, and students have to think to solve it. Blind algorithms lead nowhere.

Other things that lead nowhere are spending your leisure hours reading a math jokes blog. But since you’re here…

Why did the student put his homework in a fish bowl?
He was trying to dissolve an equation.

An engineer thinks that his equations are an approximation to reality. A physicist thinks reality is an approximation to his equations. A mathematician doesn’t care.

 

 

 

April 22, 2016 at 2:56 pm Leave a comment

Mathiest Fortnight of 2016

Monday, April 4, 2016, was Square Root Day, because the date is abbreviated 4/4/16, and 4 × 4 = 16. But if you’re a faithful reader of this blog, then you already knew that, because you read all about it in Monday’s post, Guess the Graph on Square Root Day.

But it doesn’t end there. It ain’t just one day. Oh, no, friends… this is a banner week. Or, really, a banner two weeks.

April 2016 Math

Tomorrow, April 8, 2016, is a geometric sequence day, because the date is 4/8/16, and 4 × 2 = 8, and 8 × 2 = 16.

And Saturday, April 9, 2016, is a consecutive square number day, because the month, day, and year are consecutive square numbers. Square number days, in which each of the month, day, and year are all square numbers — not necessarily consecutive — are less rare; there are 15 of them this year. But among them is 1/4/16, which rocks the intersection of square number days and geometric sequence days. (That’s right — I said “rocks the intersection.”)

And then Sunday, April 10, 2016, is an arithmetic sequence day, because 4, 10, and 16 have a common difference of 6. Though honestly, arithmetic sequence days are a dime a half-dozen; there are six of them this year.

Next Monday, April 12, 2016, is a sum day, because 4 + 12 = 16. Again, ho-hum. There are a dozen sum days this year, and there will be a dozen sum days every year through 2031.

And just a little further in the future is Friday, April 16, 2016, whose abbreviation is 4/16/16, and if you remove those unsightly slashes, you get 41,616 = 2042. I’m not sure what you’d call such a day, other than awesome.

Admittedly, some of those things are fairly common occurrences. But, still. That’s six calendar-related phenomena in a thirteen-day period, which may be enough mathematic-temporal mayhem to unseat the previously unrivaled Mathiest Week of 2013.

Partially, this blog post was meant to enlighten and entertain you. But mostly, it was meant to send numerologists off the deep end. Mission. Accomplished.

You’ve endured enough. Here are some calendar-related jokes for you…

Did you hear about the two grad students who stole a calendar?
They each got six months!

I was going to look for my missing calendar, but I just couldn’t find the time.

What do calendars eat?
Dates.

April 7, 2016 at 5:55 am 1 comment

Guess the Graph on Square Root Day

Today is Opening Day in Major League Baseball, and 13 games will be played today.

It’s also Square Root Day, because the date 4/4/16 transforms to 4 × 4 = 16.

With those two things in mind, here’s a trivia question that seems appropriate. Identify the data set used to create the graph below. I’ll give you some hints:

  • The data set contains 4,906 elements.
  • It’s based on a real-world phenomenon from 2015.
  • The special points marked by A, B, and C won’t help you identify the data set, but they will be discussed below.

Got a guess?

Home Run DistancesNo clue? Okay, one more hint:

  • The horizontal axis represents “Distance (Feet)” and the vertical axis represents “Frequency.”

Still not sure? Final hints:

  • Point A on the graph represents Ruben Tejada’s 231-foot inside-the-park home run on September 2, 2015.
  • Point B on the graph represents the shortest distance to the wall in any Major League Baseball park — a mere 302 feet to the right field fence at Boston’s Fenway Park.
  • Point C represents the longest distance to a Major League wall — a preposterous 436 feet to the deepest part of center field at Minute Maid Park in Houston.

Okay, you’ve probably guessed by now that the data underlying the graph is the distance of all home runs hit in Major League Baseball during the 2015 season. That’s right, there were 4,906 home runs last year, of which 11 were the inside-the-park variety. The distances ranged from 231 to 484 feet, with the average stretching the tape to 398 feet, and the most common distance being 412 feet (86 HRs traveled that far). The data set includes 105 outliers (based on the 1.5 × IQR convention), which explains why a box plot of the data looks so freaky:

Box Plot - Home Runs

The variety of shapes and sizes of MLB parks helps to explain the data. Like all math folks, I love a good graphic, and this one from Louis J. Spirito at the Thirty81Project.com is both awesome and enlightening:

Stadia Overlap

click the image to see the full infographic

Here are some more baseball-related trivia you can use to impress your friends at a cocktail party or math department mixer.

  1. Who holds the record for most inside-the-park home runs in MLB history?
    Jesse Burkett, 55 (which is 20 more than he hit outside-the-park)
  2. Which stadium has the tallest wall?
    The left field fence at Fenway Park (a.k.a., the “Green Monster”) is 37 feet tall.
  3. Which stadium has the shortest wall?
    This honor also belongs to Fenway Park, whose right field wall is only 3 feet tall.
  4. Although only 1 in 446 home runs was an inside-the-park home run in 2015, throughout all of MLB history, inside-the-park home runs have represented 1 in ____ home runs.
    158
  5. Name all the ways to get on first base without getting a hit.
    This is a topic of much debate, and conversations about it have taken me and my friends at the local pub well into the wee hours of the morning. I have variously heard that there are 8, 9, 11, and 23 different ways to get on base without getting a hit. I think there are 8; below is my list.
    (1) Walk
    (2) Hit by Pitch
    (3) Error
    (4) Fielder’s Choice
    (5) Interference
    (6) Obstruction
    (7) Uncaught Third Strike
    (8) Pinch Runner
  6. What is the fewest games a team can win and still make the playoffs?
    39. The five teams in a division play 19 games against each of the other four teams in their division. Assume that each of those teams lose all of the 86 games against teams not in their division. Then they could finish with 39, 38, 38, 38, and 37 wins, respectively, and the team with 39 wins would make the playoffs by winning the division.
  7. Bases loaded in the bottom of the ninth of a scoreless game, and the batter hits a triple. What’s the final score of the game?
    1-0. By rule, the game ends when the first player touches home plate.
  8. In a 9-inning game, the visiting team scores 1 run per inning, and the home team scores 2 runs per inning. What is the final score?
    16-9. The home team would not bat in the bottom of the ninth, since they were leading.

April 4, 2016 at 4:04 am 2 comments

Mathegories

In case you missed it, the following mathy challenge was presented by Will Shortz as the NPR Sunday Puzzle on February 28:

Find two eight-letter terms from math that are anagrams of one another. One is a term from geometry; the other is from calculus. What are the two words?

Will ShortzThe irony of this puzzle (for me) appearing on that particular Sunday is that five days later, I delivered the keynote presentation for the Virginia Council of Teachers of Mathematics annual conference, and I had included the answer to this puzzle as one of my slides. I wasn’t trying to present an answer to the NPR Puzzle; I was merely showing the two words as an example of an anagram. The following week, Will Shortz presented the answer as part of the NPR Sunday Puzzle on March 6.

SPOILER:
Slide from My Presentation
(aka, the answer)

What I particularly enjoyed about the March 6 segment was the on-air puzzle presented by Shortz. He’d give a category, and you’d then have to name something in the category starting with each of the letters W, I, N, D, and S.

I’ve always heard that good teachers borrow, great teachers steal. So I am going to blatantly pilfer Shortz’s idea, then give it a mathy twist.

I’ll give you a series of categories. For each one, name something in that category starting with each of the letters of M, A, T, and H. For instance, if the category were State Capitals, then you might answer Madison, Atlanta, Topeka, and Harrisburg. Any answer that works is fine. But for many of the categories, you’ll earn bonus points for mathy variations. For instance, if the bonus rule were “+1 for each state capital that has the same number of letters as its state,” then you’d get two points for Atlanta (Georgia) and Topeka (Kansas), but only one point for Madison (Wisconsin) and Harrisburg (Pennsylvania).

There are nine categories listed below, and the maximum possible score if all bonuses were earned would be 79 points. I’ve listed my best answers at the bottom of this post, which yielded a score of 62 points. Can you beat it? Post your score in the comments.

Want to play this game with friends or students.
Download the PDF version.

 

Movie Titles
(+1 for a math movie)
M _____
A _____
T _____
H _____

Historical Figures
(+1 if the person is a mathematician or scientist)
M _____
A _____
T _____
H _____

Games
(+1 if the game is mathematical)
M _____
A _____
T _____
H _____

School Subjects
(+1 for mathematical subjects)
M _____
A _____
T _____
H _____

Words with One-Word Anagrams
(+1 if it’s a math term)
M _____
A _____
T _____
H _____

Words Containing the Letter “Q”
(+1 if it’s a math term)
M _____
A _____
T _____
H _____

Math Terms
(+3 if all four terms are related, loosely defined as “could be found in the same chapter of a math book”)
M _____
A _____
T _____
H _____

Words Containing the Letters M, A, T, and H
(+1 if the letters appear in order, though not necessarily consecutively; +2 if consecutive)
M _____
A _____
T _____
H _____

Words with a Single-Digit Number Word Inside Them
(such as asinine, but -1 if the number word is actually used numerically, such as fourths; +2 if the single-digit number is split across two or more syllables)
M _____
A _____
T _____
H _____

 


The following are my answers for each category.

Movie Titles
Moebius, Antonia’s Line, Travelling Salesman, (A) Hill on the Dark Side of the Moon
(8 points)

Historical Figures
Mandelbrot, Archimedes, Turing, Hypatia
(4 points)

Games
Mancala, Angels and Devils, Tic-Tac-Toe, Hex
(8 points)

School Subjects
Mathematics, Algebra, Trigonometry, History
(7 points)

Words with One-Word Anagrams
mode (dome), angle (glean), triangle (integral), heptagon (pathogen)
(8 points)

Words Containing the Letter “Q”
manque, aliquot, triquetrous, harlequin
(6 points)

Math Terms
median, altitude, triangle, hypotenuse
(7 points)

Words Containing the Letters M, A, T, and H
ma
tch, aromatherapy, thematic, homeopathic
(8 points)

Words with a Single-Digit Number Word Inside Them
mezzanine, artwork, tone, height
(6 points)

March 25, 2016 at 1:46 pm Leave a comment

How Dumb Are You?

How Smart Are YouI recently purchased the book How Smart Are You? Test Your IQ for the same reason that I always purchase books like this — often, there are one or two gems buried amid a pile of mundane, mind-numbing questions.

Having just finished the last quiz, here’s all you need to know about this book:

  • I found it on the discount table at Barnes and Noble.
  • There is a picture of a wise, all-knowing owl on the front cover. (Ooh, an owl! I feel smart already!)
  • The tag line on the cover reads, “Calculate Your IQ in Minutes,” yet the Introduction states, “Your scores will not reflect your actual intelligence.”

When it comes to measuring your IQ using this book, the following scale will be more effective than anything you’ll find between the covers:

Did You Buy this Book?
  IQ Score  
Bought < 75
Didn’t > 125

The book contains 50 quizzes with 10 questions each. Each question is worth 16.5 points, so your IQ is found by multiplying the number correct on a given quiz by 16.5.

I hate to deliver the bad news.
The results of your IQ test have come back negative.

Sadly, there were no gems among the 500 questions in the book. (Honestly, I found it more difficult to calculate my score than to answer most of the questions.) Yet there were quite a few duds. And that’s where we’ll start today’s story.

One question asked the reader to identify the next number in the series:

5, 13, 21, 29, 37, 44, …

You may notice that 5 + 8 = 13, 13 + 8 = 21, and 21 + 8 = 29, so you might think that the rule is “add 8.” But 37 + 8 ≠ 44, so the pattern fails. You don’t even need to check the addition, though; since the first term is odd and the common difference is even, all terms must be odd. The number 44 should have stuck out like a sore thumb to any editor worth his salt. Yet that did not stop the author from listing 44 + 8 = 52 as the correct answer.

Similarly, another problem asked:

A high school has 40 students in its senior class. Forty percent of the seniors are taking physics, 30 percent are taking chemistry, and 10 percent are taking neither. How many seniors are taking neither physics or chemistry? (Ed. note: emphasis added.)

You might first think that 4 students are taking neither physics nor chemistry (nevermind that the problem used or instead of nor), since the problem says that 10% are taking neither, and 10% of 40 is 4. Upon seeing the correct answer listed as 16 students, you might then think, “What the f**k?” And that would be a justifiable reaction. I suspect that this was meant to be one of those questions where the numbers in the three groups adds to more than 100%, so the overlap becomes important, but this problem is an epic fail as presented.

Some people should have to pass an IQ test
to drive or reproduce. Fail the test,
you get birth control and a bus pass.

A little later, on a quiz titled “Unscramble the Letters I,” readers were directed to unscramble the letters

delif

to create an English word or name.

The Internet Anagram Server says that there are three: field, filed, flied. Finding one of them without the Internet seems like a reasonable challenge. But within the book, the problem is presented as a multiple-choice question:defil - AnagramOh, my. Anyone smart enough to read a book would see immediately that fled doesn’t have enough letters, flies has an s instead of the requisite d, and delight has too many letters. How many people have been misled by this quiz, scoring a 165 and then thinking that they were Harvard material?

My favorite in this section, though, was the scrambled-letter collection

lydarceptt

which I immediately recognized to be pterodactyl, but then thought, “No, wait, there’s no o.” Yet pterodactyl was the only reasonable option among the four answer choices (Pericles, lethargic, pterodactyl, and pictogram), so I ignored the omission and collected another perfect score of 165. (Yay, me!)

As I said above, there were no gems, but I’ll end with the only problem in the entire book that I even mildly enjoyed:

A car traveled 281 miles in 4 hours and 41 minutes. What was the car’s average speed in miles per hour?

This one was also presented as a multiple-choice question, but it’s more fun to solve without the options. Have at it.

Savage Chickens IQ Test

March 2, 2016 at 5:19 am 2 comments

Angle of Opportunity

My wife and I noticed that one of our sons has been getting his pants wet while urinating. He’s 8; these things happen. But when it occurred twice on consecutive days, we had reason for concern. When we inquired, he explained, “Sometimes when I start to pee, I hit the back of the seat. So I push my penis down, but then I hit the front of the toilet, and the pee ricochets and gets my pants wet.”

My wife began to pursue a line of investigative questioning, but I stopped her. “This is just simple geometry,” I explained.

I could have predicted my wife’s reaction. She said:

Not everything has to be a math problem. Especially this.

Even if that were true (it’s not), this situation still begs for some trigonometric analysis.

I’m just over 6 feet tall, so my fire hose is approximately 20″ above the toilet when I urinate. As shown in Figure A, when I stand a reasonable horizontal distance from the commode, my angle of opportunity is approximately 30°.

Adult Peeing

Figure A.

My son, on the other hand, barely clears 4 feet. His water gun is less than 6″ above the toilet when he urinates, so his angle of opportunity is a mere 20°, as illustrated in Figure B.

Kid Peeing

The images clearly indicate why mothers tell their sons (and husbands), “Stand closer to the toilet when you go!” Doing so increases the angle of opportunity and thus decreases the likelihood of a “clean-up in Aisle 3.”

But more importantly, the above images and some quick trig calculations show that an adult male — who probably has greater control than a young boy, anyway — also has a 50% greater range through which to aim when making a deposit.

Upon completing my explanation, I turned to my son. “Though it may be harder for you to hit the mark, that doesn’t excuse peeing on your pants. I think you need to be more careful.”

I then addressed my wife. “I also think we need to cut him a little slack on this one.”

“And I think,” she said, “that you are absolutely unbelievable.”

With that, she excused herself.

I’m not sure where she went, but I suspect it was to text one of her friends about how lucky she was: not only is her husband good at math, but he can apply it in extremely esoteric situations.

Rather remarkably, there has actually been serious scientific investigation into this phenomenon:

More importantly, there are a number of jokes at the intersection of math and urination:

Why do statisticians choose the last urinal?
Because there’s only a 50% change of being splashed by someone else.

What’s in the toilet of the math department restroom?
A natural log.

What does a mathematician call a toilet seat?
An ass-toroid.

February 25, 2016 at 9:32 am Leave a comment

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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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