## Posts tagged ‘golf’

### I’m Playing Baaas-Ket-Baaall

I recently had a meeting at the National Basketball Association (NBA) offices in New York City. I had gotten very excited about this meeting, thinking maybe I’d bump into Lebron or Kobe or Shaq or Dr. J or Jerry West or David Stern. (It *could* happen, ya know. Not so long ago, I bumped into Brooke Shields while attending a meeting for MoMath. All things are possible in NYC.)

But irony of ironies… when I arrived, I met no one famous; rather, one of the NBA staffers wanted to meet *me* because * Math Jokes 4 Mathy Folks* is his mom’s coffee table book. She’s a retired chemical-cum-mechanical engineer, so geeky jokes are her ilk.

Three engineers are arguing about God’s profession.

The first says, “God has to be a mechanical engineer. Look at the design of the joints and muscles.”

“No, no,” said the second. “Look at the central nervous system. All that wiring? Surely, God is an electrical engineer.”

“I think you’re both wrong,” said the third. “He’s got to be a civil engineer. Who else would put a waste management facility in the middle of a recreation area?”

Now, I know that this story likely sounds like an elaborate set-up.

Yo momma is so dorky, she reads

Math Jokes 4 Mathy Folks.

Well, it’s not. All of this is true.

The wonderful young man who wanted to meet me was Daniel Feinberg. I asked about his mother’s favorite joke from *Math Jokes 4 Mathy Folks*, and he told me it was this one (which is sometimes known as the Pizza Theorem):

Via email, Daniel told me:

It’s funny, because she [Daniel’s mom] hadn’t taken a look at the book in some time, and when I asked her for her favorite joke, she got sucked into reading the entire thing — again.

Now *that’s* a nice compliment.

Daniel isn’t an engineer or even a math guy. He loves golf, though, and his favorite joke from *Math Jokes 4 Mathy Folks* is:

A pastor, a doctor, and a mathematician were stuck behind a slow foursome while playing golf. The greenskeeper noticed their frustration and explained to them, “The slow group ahead of you is a bunch of blind firemen. They lost their sight saving our clubhouse from a fire last year, so we always let them play for free.”

The pastor responded, “That’s terrible! I’ll say a prayer for them.”

The doctor said, “I’ll contact my ophthalmologist friends and see if there isn’t something that can be done.”

And the mathematician asked, “Why can’t these guys play at night?”

Incidentally, Joshua Ferris included this same joke in his book *To Rise Again at a Decent Hour*, though the main character tells it with a priest, a minister, and a rabbi. Go figure.

I’d like to thank Daniel and his mom for their continued support. Hearing that MJ4MF made even one person smile is enough to think that it was worth writing.

Before you go, here are some basketball-related math jokes. Or maybe they’re math-related basketball jokes. Whatever. Enjoy.

What do basketball players call the last occurrence of the function that gives the greatest integer less than or equal to

x?

The Final Floor.What do athletes playing basketball and students taking a math test have in common?

They both dribble.What’s the difference between the Knicks and a dollar bill?

You can get four quarters from a dollar bill.

Okay, maybe that last one isn’t very mathy, so here’s a mathy quote from basketball commentator and former coach Doug Collins:

Any time Detroit scores more than 100 points and holds the other team below 100 points, they almost always win.

Almost?

### Golf Is a Good Walk Ruined

The title of this post is a quote attributed to Mark Twain. I would amend it as follows:

Golf may be a good walk ruined — but it’s a good time to think about math.

Not too long ago, I attended a conference at the Asilomar Conference Center on the Monterey Bay Peninsula in California. The property is adjacent to beautiful 17-Mile Drive and historic Pebble Beach. With some free time on the last afternoon, I decided to treat myself to a round of golf.

“Hello, this is Edie. Thanks for calling Pebble Beach Golf Club. How can I help you?”

“Hi, Edie. I’m wondering if I can get on the course to play 9 holes today.”

“You sure can,” she said, “but the price is the same for 9 or 18 holes.”

“Oh, okay. And what’s the price?”

“$495,” Edie said matter-of-factly.

I did a quick mental calculation, and I realized that the price would be $55 per hole.

What I said: “On second thought, Edie, I’m not sure I’ll have enough time today. Let me call back if my schedule opens up.”

What I thought: “Are you f**kin’ kiddin’ me?”

So instead of playing Pebble Beach, I found an executive course in Cupertino where I played 9 holes, rented clubs, and bought six golf balls, a bag of tees, and a new golf glove — all for less than $50.

Not only does this incident represent an exercise in fiscal responsibility, it also brought to mind divisibility rules. For instance, I realized that 495 was divisible by 9 because 4 + 9 + 5 = 18.

The rule for divisibility by 9 is rather easy to implement: just add the digits. If the result is divisible by 9, then the original number is divisible by 9, too.

A couple of weeks ago, a colleague told me that she and some friends had discovered an elegant rule for divisibility by 7. However, she was unwilling to share the method with me — she said I’d have more fun if I discovered it on my own. (I simultaneously loved and loathed her for that.)

I knew a rule for divisibility by 7, I discovered an inelegant method, and I discovered another method that was less inelegant. I’ll share my three methods below, but if you know (or discover) a different method, please share.

**The Method I Already Knew**

The rule for divisibility by 7 that I had heard before, and that can be found easily via Google, works as follows:

- Remove the units digit, and double it. (If the original number was 10
*m*+*n*, where*m*and*n*are positive integers, you’d calculate 2*n*.) - Subtract the result of Step 1 from the remaining number. (That is, you’d find
*m*‑ 2*n*.) - Repeat Steps 1 and 2 until you can determine if the result is a multiple of 7. If it is, then the original number is a multiple of 7, too.

This is best shown with an example. Let’s say you want to know if 8,603 is divisible by 7. Then first find 860 ‑ 2(3) = 854. Since it may not be obvious that 854 is a multiple of 7, repeat the procedure: 85 ‑ 2(4) = 77. Because 77 is a multiple of 7, then 8,603 must be a multiple of 7, too.

The problem with this procedure is that it takes too long for big numbers.

** The Highly Inelegant Method That I Devised**

Take the number, and continually subtract known multiples of 7. For instance, again using 8,603, first remove 7,000 to leave 1,603. Then remove 1,400 to leave 203. Then remove 210 to leave ‑7, which is a negative multiple of 7. So that means 8,603 must be a multiple of 7, too.

Since any number of the form 7 × 10* ^{k}* is a multiple of 7, a time-saving step in this process is to reduce every digit in the original number by 7. For 8,603, that means reduce 8 to 1 to leave 1,603. That’s the same as subtracting 7,000. But for a bigger number like 973,865, that shortcut could be implemented three times to leave 203,165, which might help a little. Taking this even further, remove other multiples of 7; for instance, since 16 ‑ 14 = 2, you could further reduce the number to 203,025.

I rather like this method for its simplicity, but it also takes too long.

**The Less Inelegant Method That I Found **

The reason that the rule for divisibility by 9 works is that every power of 10 is 1 more than a multiple of 9. Consequently, when a number of the form *m* × 10* ^{k}* is divided by 9, the remainder will be

*m*. For instance, when 7,000 is divided by 9, the remainder is 7; when 300 is divided by 9, the remainder is 3; and, when 80 is divided by 9, the remainder is 8. So if you subtract a lot of 9’s from 7,380, you would be left with 7 + 3 + 8 = 18 as the remainder, and since that result is a multiple of 9, then 7,380 is a multiple of 9, too.

This same idea can be applied for divisibility by 7.

- When you divide a number of the form
*m*× 10^{6k}by 7, the remainder will be*m*. - When you divide a number of the form
*m*× 10^{6k + 1}by 7, the remainder will be 3*m*. - When you divide a number of the form
*m*× 10^{6k + 2}by 7, the remainder will be 2*m*. - When you divide a number of the form
*m*× 10^{6k + 3}by 7, the remainder will be 6*m*. - When you divide a number of the form
*m*× 10^{6k + 4}by 7, the remainder will be 4*m*. - When you divide a number of the form
*m*× 10^{6k + 5}by 7, the remainder will be 5*m*.

You can then determine if a number is divisible by 7 by multiplying the units digit by 1, the tens digit by 3, the hundreds digit by 2, and so on, following the sequence 1, 3, 2, 6, 4, 5, as given above. If the result is a multiple of 7, the original number is, too.

As an example, again consider 8,603. Then calculate

1(3) + 3(0) + 2(6) + 6(8) = 63.

Since the result is a multiple of 7, then 8,603 is a multiple of 7, too.

**What You Got?**

Those are my three methods. As I said above, the third is less inelegant that the first two, but I still wouldn’t call it elegant.

Have you got a rule for divisibility by 7 that’s better than any of these? Do tell!

### Math Jokes for National Sleep Day

If you like sleep, boy, have we got some holidays for you.

Today is National Sleep Day. eHow.com has a list of things to do today, and the first thing on their list — shocker! — is sleep. (Okay, technically they list “sleep in,” but doesn’t that seem obvious for this particular holiday?)

In the U.S., February 19 is National Sleep In Day; in Britain, it’s October 31. One blogger declared that May 11 should be National Sleep Naked Day.

March 3-9, 2012, is National Sleep Awareness Week, which occurs annually the week before the change to Daylight Savings Time.

And if you’re one of those folks who really likes to extend your holidays, you don’t need to limit your love of sleep to just one day or even a week. November is National Sleep Comfort Month, and May has been dubbed National Sleep Better Month.

Holy criminy! Is all of this really necessary? Luckily, mathy folks really like to sleep.

What do mathematicians sleep on?

Matrices.

Mathy folks also appreciate that others need sleep, too.

A math teacher is someone who talks in someone else’s sleep.

Married mathy folks have a keen awareness of how much sleep they need.

A single mathematician was asked, “If you go to bed eight hours before you have to wake up, and your girlfriend wants to have two hours of sex, how much sleep will you get?” He answered, “6 hours.”

When a married mathematician was asked the same question about having two hours of sex with his wife, he responded, “7 hours, 57 minutes. Why does it matter what she wants?”

Finally, a joke about the other meaning of the word *sleep*.

Wife:“If I died, would you get married again?”

Mathematician:“No.”

Wife:“Why not? Don’t you like being married?”

Mathematician:“Of course, I do.”

Wife:“Then why wouldn’t you remarry?”

Mathematician:“Fine, I’ll remarry.”

Wife:“You would?”

Mathematician:(groan)

Wife:“Would you live in our house, too?”

Mathematician:“Sure, it’s a great house.”

Wife:“Would you sleep with her in our bed?”

Mathematician:“Where else would we sleep?”

Wife:“Would you let her drive my car?”

Mathematician:“Probably. It’s brand new.”

Wife:“And would you let her use my golf clubs?”

Mathematician:“No, she’s left-handed…”