## Archive for January, 2020

### This is a Blog Post

One of my favorite warm-ups to use in presentations is the following:

This sine has threee errors.

It’s a bit of a joke grenade… pull the pin, wait five seconds, eventually some folks will start to chuckle. In addition to inciting laughter, it also works well as a formative assessment.

One of my favorite books is by Demetri Martin:

One of my favorite jokes is from Steven Wright:

I went to a bookstore and asked the woman, “Where’s the self-help section?” She said that if she told me, it would defeat the purpose.

One of my favorite comics is from Randall Munroe:

One of my favorite experiences happened at a Chinese restaurant:

And one of my favorite puzzles is from Gödel, Escher, Bach:

There are __ 0s, __ 1s, __ 2s, __ 3s, __ 4s, __ 5s, __ 6s, __ 7s, __ 8s, and __ 9s in this sentence.

I love that this puzzle can be solved with iteration: put in some numbers, see how that affects things and adjust, see how that affects things and adjust, ad nauseam, until you either find a solution, or until you run into an infuriating cycle and have to start over with new seed values.  For instance,

 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 → 2, 2, 2, 2, 2, 2, 2, 2, 2, 2 → 1, 1, 10, 1, 1, 1, 1, 1, 1, 1 → 2, 10, 1, 1, 1, 1, 1, 1, 1, 1 → 2, 9, 2, 1, 1, 1, 1, 1, 1, 1 → …

If you haven’t figured it out by now, my favorite things often include self‑reference. I speak in self-referential sentences when I go to job interviews…

At the end of my job interview, the interviewer asked, “Finally, what is the question you’d least like to be asked during this interview?” I replied, “That was it.”

And when visiting my therapist…

I’m trying to be less self-deprecating, but I really suck at it.

Perhaps the best self-referential (and self-deprecating) line in history comes from Groucho Marx:

I would never join a club that would have me as a member.

But there are no shortage of self-referential jokes in the world.

I never make predictions, and I never will. (Paul Gascoigne)

What would the value of 190 in hexadecimal be?

A student asked, “What is the best question to ask, and what is the best answer to that question?” The teacher responded, “The best question is the one you just asked, and the best answer is the one I just gave.”

I am the square root of -1. Who am i?

No! No! No! I am not in denial!

When you’re right 90% of the time, you needn’t worry about the other 5%.

The reciprocal of the square root of 2 is half of what number?

It’s bad luck to be superstitious.

Twenty-nine is a prime example of what kind of number?

Break every rule.

### More HIPE

Nearly five years ago, I wrote about HIPE, a parlor game in which one person gives a particular string of letters, and the other people in the parlor try to guess a word with that same string of letters (consecutively, and in the same order).

Well, I recently rediscovered Can You Solve My Problems? by Alex Bellos, and I was pleasantly surprised to find that he included four HIPEs in that book:

1. ONIG
2. HQ
3. RAOR
4. TANTAN

The fourth is one that I had included in my previous post, Don’t Believe the HIPE, and all are good enough that they deserve wide distribution.

Just for fun, here’s a new list of HIPEs that might prove interesting.

• SSP
• LWE
• NUSCU
• CUU
• CTW
• KGA
• UIU
• XII

In an effort to collect a bunch of excellent HIPEs, I’m asking for your help. If you play the game with friends and discover a particularly delectable combination of letters, please share below or at https://forms.gle/otddCw1uLeDALrMo7.

### Truth, Lies, and Math in Portland

The city that I now call home — Portland, OR — is the most beautiful city in the country. With views of Mt. St. Helens to the north, Mt. Adams to the northeast, Mt. Hood to the east, and powerful rivers through the middle of town, it’s hard to look in any direction without having your breath stolen.

As it turns out, Portland is also the smartest city in the country. This fact is irrefutable, per the following data.

Although the data suggests that Portland might only be the second-smartest city in the country — Portland lags slightly behind Boston in per capita sales of Math Jokes 4 Mathy Folks — Stumptown leapfrogs Beantown because not a single person in Portland deigns to root for the Patriots.

The exemplary intelligence of Portlandians is only one of the many things I’ve discovered since moving to the Pacific Northwest. I’ve also learned that Portland is a beer Mecca; that, despite its reputation, the weather in Portland is far from terrible and, in fact, quite to my liking; it has some cool parks; and, Portland has a lot of bikes and a lot of bridges.

Beer

As a beer lover, I was ecstatic to hear that Portland had the most craft breweries of any city in the world.

Unfortunately, that was an old statistic, and Portland, OR, currently ranks #8 nationally in terms of craft breweries per capita:

1. Portland, ME
2. Asheville, NC
3. Bend, OR
4. Boulder, CO
5. Kalamazoo, MI
6. Vista, CA
7. Greenville, SC
8. Portland, OR
9. Pensacola, FL
10. Missoula, MT

The “other Portland” garners the top spot on the list. But it seems to me that if the list were culled to show only those cities where people actually want to live, the real Portland would again be near the top. (Asheville and Boulder absolutely give Portland a run for their money. But Kalamazoo and Vista? C’mon, now!)

Weather

Portland is known for gray skies and rain. But compare Portland to my previous hometown, Washington, DC.

The graphs below show that DC is warmer and wetter in the summer, but colder and drier in the winter.

But let’s dig into those numbers a little.

The average temperature in the two cities is remarkably similar, with Portland averaging 54.5°F and Washington, DC, averaging 55.7°F. But the hottest days are hotter in DC, and the coldest days are colder in DC. The temperate oceanic climate in Portland explains the cooler summers, the warmer winters, and the incredibly high number of homeless people.

Admittedly, Portland has more days of rain than Washington, DC — 156 to 115, in fact — but it receives a significantly smaller amount of rainfall — 36.0″ to 40.8″, a difference of nearly five inches.

Portland trails in hours of sunshine by roughly 10%, with 2,341 hours compared to DC’s 2,528. But Portland also has fewer days of snow per year, just 2.2 to DC’s 8.0, and much less accumulation — 3.0″ in Portland to a whopping 14.5″ in the nation’s capital.*

But rain, snow, sun, and temperature aside, there may be one statistic that is more important than all the others: Washington, DC, has significantly more days of Donald Trump, averaging over 300 per year since 2016; but since becoming President, Trump has spent nary a minute in Oregon.

Parks

Portland boasts Mill Ends Park, which holds the Guiness World Record for smallest park on the planet.

With a diameter of just 24″, the total area of Mill Ends Park is exactly π square feet, or approximately 0.000 072 acres.

Bikes

Portland has 94 miles of neighborhood greenways, 162 miles of bike lanes, and 85 miles of bike paths. That’s 341 biker‑friendly miles, which explains why more than 22,000 people ride their bikes to work every day. Over six percent of Portland’s commuters bike to work, which is twelve times the national average.

The joke in Portland is that, when you step off an airplane at PDX, they hand you a rain jacket and a dog. But if they really want folks to fit in, they better start doling out bikes, too.

Bridges

The Willamette (pronounced wuh-LAM-it, not WILL-uh-met) River separates the east and west sides of Portland, and it’s spanned by twelve bridges. When the Hawthorne Bridge was built in 1910, it was one of the first vertical-lift bridges anywhere in the country; now, it’s the last one still in operation. The Tilikum Crossing Bridge was the country’s first ever multi-modal bridge that accommodated light rail, streetcar, buses, and pedestrians — but not private automobiles. And the St. John’s Bridge, known for its 400-feet high, twin Gothic-style arches, previously held the records for the world’s longest pre-stressed twisted rope cables as well as the tallest reinforced concrete pier in the world.

Every morning as I cross the Sellwood Bridge, I look north to the smartest, drunkest, rainiest, most beautiful city in the country, and there’s no place I’d rather be.

* Every Portland resident who has relocated from some other part of the country will make a similar comparison between the weather in Portland and the weather in the city where they used to live. This is nothing more than rationalizing the decision to move to a city that only gets 144 days of sunshine a year.**

** Every Portland resident will also tell folks in other cities how bad the weather is, in an attempt to discourage others from moving to this amazing city. In short, they don’t want you here. I suspect, in fact, that they didn’t (and maybe still don’t) want me here. But too late, I’m staying. You, on the other hand, shouldn’t even think of coming here. I promise, you’ll hate it.

### 20 Math Problems for 2020

Happy New Year!

• It’s a leap year — yay!
• It’s the year of the rat — squeak!
• It’s an election year — okay, maybe it’s not that great of a year after all.

To get your mind thinking about something other than the associated realities of that last bullet, here are 20 problems to prepare you for the next 366 days.

1. What’s the difference between the number of positive integer factors of 2020 and the number of positive integer factors of 2020?
2. If all of the numbers from 1 to 2,020 were written down, how many digits would be used?
3. If all of the numbers from 1 to 2,020 were spelled out, how many letters would be used?
4. The numbers 1 through 2,020 are written on a whiteboard. At every stage, two numbers (say, a and b) are erased from the whiteboard and replaced with the sum a + b + 1. For example, if 187 and 2,013 were erased, then 187 + 2,013 + 1 = 2,201 would be written on the whiteboard. This process is repeated until a single number remains on the whiteboard. What is the number?
5. How many positive integers are less than the square root of 2,020?
6. How many different rectangles with integer side lengths and an area of 2,020 square units are possible?
7. A lighthouse is perched on the cliff of a rocky beach. Standing in the lantern room of the lighthouse, you are approximately 2,020 feet above the surface of the ocean below. How far can you see to the horizon?
8. A rectangular prism with integer edge lengths has a volume of 2,020 cubic centimeters. What is the maximum possible surface area of this solid?
9. Mike made two initial bank deposits on Monday and Tuesday. Then every day for the rest of the week, he deposited an amount equal to the sum of the previous two days’ deposits. If he deposited \$2,020 on Saturday, and his deposit on Monday was less than \$10, what was the amounts of his deposit on Tuesday?
10. What’s the sum of 101 + 202 + 303 + … + 2,020?
11. How many postive, four-digit numbers can be formed with the digits 2, 0, 2, and 0?
12. Saying that someone has 20/20 vision means they have normal visual acuity. That is, if you have 20/20 vision, then from 20 feet away, you can see what a normal person would see clearly from 20 feet away. In general, if you have 20/n vision, then from 20 feet away, you can see what normal people would see from n feet away. A person with 20/5 vision is looking at a billboard that is a mile away, and she can clearly see the letters on the billboard. How much closer would a person with 20/80 vision need to stand to clearly see the letters on the billboard? (Assume both people are standing at the boundary of where they can read the sign clearly.)
13. A triangle has two sides of length 20. What is the maximum possible area of this triangle?
14. Using only the digit 2 and the addition symbol, you can create expressions with many different values. For instance, you could use three 2’s and one addition symbol to make 22 + 2 = 24, or you could use  eight 2’s and three additional symbols to make 222 + 22 + 22 + 2 = 268. Using this process, what is the minimum number of 2’s needed to make an expression with a value of 2,020?
15. In how many zeroes does the number 2020 end?
16. Find the smallest possible string of consecutive positive integers that have a sum of 2,020.
17. One integer is removed from the set {1, 2, 3, …, n} so that the sum of the remaining numbers is 2,020. What integer was removed?
18. What is the product of the prime divisors of 2,020?
19. What is the maximum possible product for a set of positive integers that have a sum of 2,020?
20. Which of the following chains — each consisting of regular polygons with side length 1 unit — could be extended to have a perimeter of exactly 2,020 units?

1. 849
2. 6,973 digits
3. 47,123 letters
4. 2,043,229
5. 44 integers
6. 6 rectangles
7. approximately 52.5 miles
8. 8,082 square centimeters
9. \$401 on Tuesday (and \$5 on Monday)
10. 21,210
11. 3 numbers
12. the person would need to be 1/16 mile = 330 feet from the billboard, which is 4,950 feet closer
13. 200 square units
14. 29 2’s
15. 20 zeroes
16. 402, 403, 404, 405, 406
17. 60
18. 1,010
19. 3672 × 22
20. only the squares; for n squares, the perimeter is 2n + 2, and n = 1,009 yields a perimeter of 2 × 1,009 + 2 = 2,020

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.