## Archive for July, 2013

### Riding the Gravy Train

I was recently telling a friend about the success of my book. “I don’t get it,” he said. “You write a few math jokes, and you’re riding the gravy train!”

This raises a few issues.

First of all, what the hell is a gravy train? Have they started carrying gravy by rail? Are there people at the train station with satchels of mashed potatoes, waiting for the five-fifteen to arrive?

Second, creating jokes is hard. Creating math jokes is even harder. And creating funny math jokes is nearly impossible — as anyone who reads this blog can attest.

Third, I am not riding the gravy train. According to Wiktionary, *riding the gravy train* refers to “any lucrative endeavor that generates considerable income whilst requiring little effort and carrying little risk.” My book has sold well, and I am thankful for the minor level of celebrity it has brought me. But it has **not** allowed a lifestyle change. It’s not like the profits are enough for a new car. Heck, they aren’t even enough for a new bike! Maybe a helmet, if I shop at a second-hand store.

Finally, where did the expression riding the gravy train come from? The phrase *everything else is gravy* is sometimes used to describe a situation where expenses are covered and a significant profit remains. In addition, train rides are enjoyable — while you relax in comfort, a train takes you where you want to go. Conventional wisdom says that *gravy train* is the result when you put these two phrases together.

Here’s a math joke involving trains.

Q: You board a train in Newark that travels south at 15 mph. At the same time, your friend boards a train in Trenton that travels north at 25 mph. How long before you pass each other?

A: What the hell are you doing in Jersey?

Here’s another, though you’ve probably heard this one before.

Some math and engineering students boarded a train to a convention. Each of the math majors had a ticket, but the engineering students had only one ticket between them.

The math majors were laughing about this when an engineering student shouted, “Conductor!” With that, all the engineering majors squeezed into a bathroom. The intrigued math students watched as the conductor knocked on the bathroom door and said, “Ticket, please.” The conductor took the single ticket that was slid under the door, and left.

Not to be outdone, the math students boarded the return train without a ticket. The engineers laughed.

The engineer lookout yelled, “Conductor!” All of the engineering students crowded into one bathroom, while the math majors piled into another. Then, before the conductor entered the car, one of the math majors came out of his bathroom, knocked on the engineering students’ door, and said, “Ticket, please.”

And if you like Ozzy Ozborne, or if you enjoy terrible poetry, then you might appreciate the following revised lyrics for one of Ozzy’s songs.

Gravy Train(to the tune ofCrazy Trainby Ozzy Ozborne)Gravy, for mashed potatoes

Millions of gallons ready to flo-o-o-ow

Maybe it’s not too late

To learn how to love

My liquid brown freightPotatoes so appealing

Other sides are lame —

I’m rolling down the rails on a gravy train

I’m rolling down the rails on a gravy train…

### Can’t Argue with That

My momma always told me:

Don’t break a person’s heart; they only have one. Break their bones; they have 206.

Who can argue with that logic? Here are some other logical statements with which you won’t want to argue, either.

I asked my wife what she wanted for her birthday. She said, “Nothing would make me happier than diamond earrings.” So, I got her nothing.

I find it strange that my advisor always begins conversations with me by saying, “You haven’t heard a word I’ve said, have you?”

It doesn’t matter if the glass is half empty or half full; either way, there is room for more alcohol.

I only drink twice a year: when it’s my birthday, and when it’s not.

My math teacher just fell in a wishing well. Go figure! I never knew they worked.

My advisor says I’ll never graduate because I’m lazy. But I just can’t take that kind of criticism. I was going to kill myself… but the gun’s, like, way over there.

Don’t judge a book by its cover… my math book has a picture of someone enjoying himself.

A grad student told his friend, “My girlfriend hates it when I sneak up behind her and kiss her on the cheek. But according to her lawyer, she also hates it when I call her my girlfriend.”

I got a tattoo of Chinese symbols on my arm that reads, “I don’t know. I don’t speak Chinese.” So when someone asks what it says…

Boy: I hate my math professor. He’s a terrible lecturer, he has bad breath, and he laughs at his own jokes.

Girl: Who’s your professor?

Boy: Dr. Jacoby.

Girl: Do you know who I am?

Boy: No.

Girl: I’m Dr. Jacoby’s daughter.

Boy: Do you know who I am?

Girl: No.

Boy: Good.

### How Cool is This?

A couple of riddles to warm you up for the pain you’re about to receive.

What starts with E, ends with E, and contains only one letter?

Envelope.What goes round the world but always stays in the corner?

A stamp.

I received a solicitation from American Express today that said I could “get 50,000 Membership Rewards points” by signing up for one of their cards. That sounded like a sweet deal. But not half as sweet as the mailing address that appeared on the envelope:

In case that’s too small or grainy for you, in the dashed box it reads:

Mathy Folks

XXX Xxxxxx Xxxxx

Falls Church, VA 22046-XXXX

Who knew the credit card companies had gotten so good at data mining that they know my address *and* my family’s intellectual dispositions?

### A Great Day for a Math Trick

Today is 7/11/13, and boy, have I got a great math trick for today! You’ll likely need a calculator.

- Multiply your age by 12.
- Now add the age of your spouse/brother/sister/friend/uncle/aunt/whomever.
- This should yield a three-digit number. Now, divide by 7.
- Then, divide by 11.
- Then, divide by 13.
- The result should be a number of the form 0.
*abcdef*…, with a 0 and a decimal point in front of a long string of digits. Add the**first six digits**after the decimal point.

Here’s the cool part. I don’t know your age, nor do I know the age of your spouse, brother, sister, friend, uncle, or aunt. But I do know that after you completed those steps, the result was 27.

Pretty cool, eh?

There are myriad math tricks of this ilk, but this one is my favorite. It’s based on a trick I learned from Art Benjamin, though I think the one above has more panache than his original. Decide for yourself.

- Choose a number from 1 to 70, and then divide it by 7.
- If your total is a whole number (that is, no digits after the decimal point), divide the answer by 7 again.
- Is there a 1 somewhere after the decimal point? I predict that the number after the 1 is 4. Am I right?
- Now add up the first six digits after the decimal point.

Just as with the trick above, the result will always be 27.

Regardless of which trick you prefer, have a happy 7/11! And if you’ve got a few hours to kill, you can try to solve the 7‑11 problem.

### Being All Inclusive

In the middle of a conversation with his grandmother yesterday, my six-year-old son Alex excused himself to look at an item in her house. He returned and, addressing no one in particular, announced, “There are 24 buttons shown in that picture. It’s a 4 × 6 grid.”

“I’m so sorry,” I said to my mother-in-law for raising a son who would walk away from a conversation with her. “I’m sorry to you, too,” I then said to Alex, for conditioning him to look at everything with a mathematical eye and, ostensibly, for making it impossible for him to shut if off. (It should be noted that Alex’s dad has the same affliction.)

As another example, I told the boys that if they could figure out how much change I had in my pocket, they could split it for their piggy banks. “I have two types of coins, with twice as many of one type as the other. And the value of my coins is between 20¢ and 25¢.” Alex then asked:

You mean between 20¢ and 25¢

inclusive?

And why wouldn’t he? Isn’t that the question than every normal, well adjusted six-year-old would ask in the same situation?

Taking a walk with Eli this morning, we encountered this sign:

I asked Eli, “Do you think I’d get in trouble if I were in this park at 8:30 p.m. on October 1?” He said I would, that the park is open till 9:00 p.m. through September 30, and then it switches to the early hours on October 1. I suppose I agree, but I’d still argue that the sign could be less ambiguous.

These experiences remind me of a joke.

The law of inclusion-exclusion either rules or does not rule.

### Wonders of the Math World

It was Dr. Seuss who said…

Think! Think and wonder. Wonder and think.

How much water can 55 elephants drink?

These are the things about which I think and wonder.

Ever wonder why pizza is circular, delivered in a square box, and served in triangular slices? Weird.

Divorce is like algebra.

Have you ever looked at your *x* and wondered *y*?

Ever wonder why textbook authors write problems about people who buy 58 dozen eggs at the grocery store? Or why their editors don’t edit them?

### My Wife’s Son

I’m fortunate to have Joshua Zucker as a friend and colleague. Knowing that my sons have a penchant for math, he recently sent me a set of *Got It!* cards. *Got It!* is a game in which number cards and operation cards are alternately laid out in a grid, and the object is to find a set of at least five cards (three number cards and two operation cards) that form an expression equal to a certain target number. If you find such an expression, the target card is added to your collection, and the person who collects the most target cards wins.

For instance, the grid below shows an arrangement of 36 orange cards that are to be used to form either 23 or 29 (the blue target card on the left). I’ll give you a moment to find such an expression yourself.

Tonight before dinner, my sons and I played *Got It!* for the first time, and the challenge above was one with which we were presented. In less than 10 seconds, Alex found an expression equal to 23. Starting with the 8 in the third row, first column, he constructed the following:

(8 + 3 – 1) × 2 + 3 = 23

As he explained his solution, he said, “Well, 8 + 3 – 1 is 10, times 2 is 20, plus 3… *simple*.” Part of me thought, “That’s pretty good.” But most of me thought, “Wow, did my six-year-old son really just best me in a math game and then declare that it was simple?” Sure enough, he had.

Apparently, that wasn’t sufficient, though. The next target card was 25, and Alex again found a correct expression faster than Eli or I. Eli tried to hand the target card to Alex, but Alex demurred. “No,” he said. “I’m not playing this round, so you and Daddy can get some cards.” Part of me thinks he’s just a sweet six-year-old who doesn’t want to trounce us… but most of me thinks he’s developing an attitude that needs to be nipped in the bud.

My only solace is that he’s *my wife’s son*, and I’m sure he didn’t get this from me.

This reminds me of a story.

A friend’s six-year-old son said, “Daddy, I need help with a math problem I couldn’t do at school today.”

“Sure”, the father says with a smile. “What’s the problem?”

“Well, it’s really hard. There are four ducks in a pond, and two more ducks come and join them. How many ducks are now in the pond?”

The friend stares at his son and says, “You couldn’t do that? You don’t know that 4 + 2 = 6?”

“Of course I know that,” he says. “But what’s that got to do with ducks?”