Archive for November, 2011

Problems of Convenience

The candy that my sons received while trick-or-treating all had names with references to various disciplines:

  • Baby Ruth – history; named for the daughter of President Grover Cleveland
  • Snickers – sports; named after Frank C. Mars’s favorite horse
  • 3 Musketeers – literature; named for Athos, Porthos, and Aramis from Alexandre Dumas’s novel
  • Milky Way – astronomy; named after the galaxy
  • 5th Avenue – geography; named after 5th Avenue in Reading, PA, where the candy bar was originally made

While there was no candy with references to advanced mathematics, several at least had numbers in the names. In addition to 3 Musketeers and 5th Avenue, there were also:

  • Zero
  • Take 5
  • 100 Grand

I visited several local convenience stores to find other candy bars with numbers or math in the name. Sadly, my search yielded no others. Luckily, interesting things always happen when I’m in convenience stores…

7 Eleven

A woman walks into a 7-Eleven and takes four items to the cash register. The clerk informs her that the register is broken, but he can figure the total using his calculator. The clerk then proceeds to multiply the prices together and declares that the total is $7.11. Although the woman knows the prices should have been added, not  multiplied, she says nothing — as it turns out, the result would have been $7.11 whether the four prices were added or multiplied.

There was no sales tax. What was the cost of each item?

Of course, you may be thinking, “If the four prices were multiplied together, the total would actually be 7.11 dollars4.” And you would be correct. But for the sake of the problem, it’s best not to introduce “quartic dollars” as a unit of measure. I’ll ask that you please suspend disbelief, at least until you’ve solved the problem.

The problem above involves four items, and finding its solution is quite difficult. To reduce the level of difficulty, I wondered if an analogous problem could be created that involves only three items. After an hour of playing with Excel, I was able to create such a problem.

6 Sixty

A woman walks into a 6-Sixty and takes three items to the cash register. The clerk informs her that the register is broken, but he can figure the total using his calculator. The clerk then proceeds to multiply the prices together and declares that the total is $6.60. Although the woman knows the prices should have been added, not  multiplied, she says nothing — as it turns out, the result would have been $6.60 whether the three prices were added or multiplied.

There was no sales tax. What was the cost of each item?

The problem with only three items is not significantly less difficult than the problem with four items, however, it is helped by the fact that there are two different solutions. Still, I wondered if an analogous problem could be created that involves only two items. Sure enough, one could.

8 Forty-One

A woman walks into an 8-Forty-One and takes two items to the cash register. The clerk informs her that the register is broken, but he can figure the total using his calculator. The clerk then proceeds to multiply the prices together and declares that the total is $8.41. Although the woman knows the prices should have been added, not  multiplied, she says nothing — as it turns out, the result would have been $8.41 whether the two prices were added or multiplied.

There was no sales tax. What was the cost of each item?

This last problem is far less difficult than the other two. Enjoy!

November 4, 2011 at 1:14 am Leave a comment

If You’re Happy and You Know It…

Some neighbors recently told me that childless adults are happier than parents. When I mentioned this to a different friend (who is currently trying to become a parent), his response was, “Yeah, but the graph shows that parents don’t become really unhappy until the third child.”

A quick search did not yield the graph he mentioned, but it did provide a lot of contradictory information:

  • A blog post by Philip Cohen claims that “children beget happiness, eventually.”
  • A report from the Pew Research Center claims, “married people with children are about as happy as married people without children. And unmarried people with children are about as happy as unmarried people without children.” (This chart shows that marriage is a better predictor of happiness than children.)
  • A Global Perspective on Happiness and Fertility by Margolis and Myrskyla indicates that people over 50 are happier than younger folks, regardless of the number of children; but among parents, those with 4+ kids are less happy than others.

So, I don’t know what to believe. All I know is that when my four-year-old son Eli created the following math joke last night, I was pretty happy.

What did the table say to the counter?
“Give me some numbers!”

Get it? Counters? They count!

Then today, while riding in the car, Eli’s twin brother Alex asked what language people speak in Europe. “I think they speak European,” he posited, “but Eli thinks they speak Urine.”

Who couldn’t be happy with wonderful moments like that?

For tolerating (another) story about my kids, here are a few funny quotes about happiness.

I didn’t know true happiness until I got married; but then it was too late.

Whoever said that money can’t buy happiness didn’t know where to shop. – Gertrude Stein

Happiness is good health and a bad memory. – Ingrid Bergmann

November 2, 2011 at 10:34 pm Leave a comment

Free Copy of My Book

A few days ago, a seventh‑grade math teacher and assistant baseball coach sent me the following request:

I would love to have a copy of Math Jokes for Mathy Folks, but I am financially unable to purchace it right now because my wife is unable to work and hasn’t been approved for disability.

Now, I like to think I’m a generous guy, but I am unable to send a free copy of my book to everyone who asks for it. A little‑known fact about the publishing industry: The majority of authors actually have to pay for copies of their own book. It’s an interesting percent problem. I pay 50% of retail price plus shipping to purchase copies of my book, but I then receive a 15% royalty on the discounted price of every copy I purchase. (You can do the math to figure out how many books I could give away for free before going bankrupt.)

So I sent the following reply:

Send me your favorite joke(s), mathy or not, and I’ll send you a copy of the book.

My correspondent responded quickly with three jokes, two of which I had never heard before. A copy of my book is in the mail to him, and his jokes are pasted below for your reading pleasure.

What’s a seventh grader’s favorite excuse for not doing homework?
I have a solar‑powered calculator, but yesterday it was cloudy.

The student’s second semester seemed so much like her first that she hoped she could graduate sooner by combining like terms.

How is an indecisive third‑base coach like multiplying or dividing by a negative integer?
In both cases, the sign changes.

Incidentally, you can download one chapter of Math Jokes 4 Mathy Folks for free by clicking the following button:

Pay with a Tweet

November 1, 2011 at 9:16 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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