Posts tagged ‘Celsius’

Math in France

Math in FranceDriving through the French countryside using smartphone GPS for navigation is a lot like driving through rural Pennsylvania with my redneck cousin riding shotgun — there is a significant lack of sophistication, an ample amount of mispronunciation, and myriad grammatical errors.

In Pennsylvania:

Take that there right onto See-Quo-Eye-Ay (Sequoia) Drive.

In France:

At the roundabout, take the second right toward Ow-Bag-Nee (Aubagne).

Take D51 to Mar-Sigh-Less (Marseilles).

And of course, the GPS pronounced the coastal town of Nice like the adjective you’d use to describe your grandmother’s sweater, though it should sound more like the term you’d use to describe your brother’s daughter.

I was half expecting the computer voice to exclaim,

Hey, cuz, watch this!

Otherwise, the rest of my recent week-long trip to the south of France was intellectually and often mathematically stimulating. The image below shows a -1 used to describe an underground floor (parking) in a hotel:

Elevator, -1

And though I didn’t get a picture, the retail floor of the parking garage at the Palais de Papes in Avignon was labeled 0, with the three floors below for parking labeled -1, -2, and -3.

This is a country that does not fear negative integers.

I also noticed that the nuts on fire hydrants in Aix-en-Provence were squares.

Fire Hydrant - Square

Hydrant with Square Nut

The nuts on American hydrants used to be squares, until hoodlums realized that two pieces of strong wood could be used to remove them, release water into the streets, and create an impromptu pool party for the neighborhood. As a result, pentagonal nuts are now used on most hydrants.

Alas, an adept hoodlum can even remove pentagonal nuts, so some localities have replaced them with Reuleaux triangle nuts, like the ones on hydrants outside the Philadelphia convention center, which can only be removed with a specially forged wrench.

Hydrant Reuleaux

Hydrant in Philadelphia
with Reuleaux Triangle Nut

But perhaps the most mathematical fun that France has to offer is the Celsius scale. While there, our cousins taught my sons a poem for intuitively understanding the Celsius scale:

30 is hot,
20 is nice,
10 is cold,
and 0 is ice.

And I was able to teach them a formula for estimating Fahrenheit temperatures, which is easy to calculate and provides a reasonable approximation:

Double the (Celsius) temperature, then add 30.

Or algebraically,

F = 2C + 30

The actual rule for converting from Fahrenheit to Celsius is more familiar to most students:

F = 1.8C + 32

This rule, however, sucks. It’s not easy to mentally multiply by 1.8.

My sons were not convinced that the rule for estimating would give a close enough approximation. I showed them a table of values from Excel:

Temp Conversion Actual vs Estimate

I also showed them a graph with the lines y = 1.8x + 32 and y = 2x + 30:

Celsius - Actual vs Estimate

With both representations, it’s fairly clear that the estimate is reasonably close to the actual. For the normal range of values that humans experience, the estimate is typically within 5°. Even for the most extreme conditions — the coldest recorded temperature on Earth was -89°C in Antartica, and the hottest recorded temperature was 54°C in Death Valley, CA — the Fahrenheit estimates are only off by 9° and 20°, respectively. That’s good enough for government work.

And here’s a puzzle problem for an Algebra classroom, using this information.

The Fahrenheit and Celsius scales are related by the formula F = 1.8C + 32. But a reasonable estimate of the Fahrenheit temperature can be found by doubling the Celsius temperature and adding 30. For what Celsius temperature in degrees will the actual Fahrenheit temperature equal the estimated Fahrenheit temperature?

It’s not a terribly hard problem… especially if you look at the table of values above.

June 25, 2014 at 9:39 am 2 comments

Math Coinky-Dinks

I’m a math guy, so I know that most coincidences are nothing more than people making a big deal out of something that, in fact, is quite likely. I’m not impressed when two people at a cocktail party have the same birthday or when nearly 30% of the people at that same party have a street address that begins with the digit 1.


Nor was I impressed when the Oregon newspaper The Colombian printed a winning number for the state lottery in advance. The probability that the number they accidentally printed on June 27, 2000, which was 6-8-5-5, would actually win the Pick 4 game the following day was 1/10,000. Not likely, to be sure, but not out of the question.

But is it just a coincidence that Douglas Adams claimed that 42 is “the answer to life, the universe, and everything,” and that Oreo cookies can be obtained by pressing 42 on the vending machine in my office?

And is it just a coincidence that ELEVEN + TWO = TWELVE + ONE?

Well, yeah. Probably.

But something happened yesterday that was so strange, it cannot be brushed aside as mere coincidence.

My son Alex was home sick from school. Around two o’clock, he said, “Daddy, I smell blood.” I checked to make sure he wasn’t bleeding… then I checked to make sure that I wasn’t bleeding, either. There was no blood to be found. A couple of hours later, we went to pick up his twin brother Eli at school, and Miss Vanessa at after-school care told me that Eli had an accident.

“He fell and hurt his knee,” she said, “and there was blood everywhere.”

Blood? I asked what time that happened. “Around two o’clock,” she said.


With twin boys, I suspect that there will be similar coincidences in the future. For instance, I suspect that I will one day receive a call saying that both boys were caught in a co-ed dorm after curfew. How weird would that be?

But I’m not phased. Coincidences are very common in my family. For example, my mother and father got married on the same day!

To check out some truly random statistical coincidences, click on over to

The following joke is based on a fun math coincidence.

Saul: It’s -40 outside.
Paul: Fahrenheit or Celsius?
Saul: When it’s that cold, it’s impossible to tell the difference.

It’s just a coincidence that -40° F = -40° C.

Or is it?

November 8, 2012 at 12:32 pm Leave a comment

If This is What Hades is Like, We Better Change Our Ways

It was so hot in Virginia today, I saw two fire hydrants fighting over a dog.

Truth be known, I’m travelling through California right now, so I don’t actually know how hot it was in Virginia today. But I got an email that said my wine o’ the month shipment would be delayed until the weather cools to a point where the wine won’t be in danger of spoiling. Zoiks! In California this week, it’s been rather pleasant — even chilly at night, with temps in the low 50’s.

A recent conversation with the Northern California friends we’re visiting turned to temperature conversions. John said that on international trips, he amuses himself by converting Celsius temps to Fahrenheit. I informed him that the rule “times 2 plus 30” gives an accurate estimate for temps in the typical range — it isn’t really necessary to remember the exact rule. I also shared a poem about Celsius temps that he and his wife hadn’t heard before:

30 is hot,
20 is nice,
10 is cold,
and 0 is ice.

Finally, a stupid math and weather joke.

What is the name of a person who only adds when it’s hot outside?

July 22, 2011 at 2:24 am Leave a comment

Temperature of McDonald’s Coffee, and Other Celsius Benchmarks

I am so done with cold weather. Northern Virginia had trouble breaking 40°F in January. Granted, we’re not International Falls, MN, where the temperature had trouble surpassing the legal drinking age, but I am still ready for spring.

In January 2005, I went skiing near Montreal. At the bottom of the mountain, a thermometer showed the temperature to be ‑25°C. Next to the thermometer was a sign announcing that the temperature at the top of the mountain was ‑20°C. My buddy said, “Quick, let’s get on the lift. It’s 5° warmer at the top.”

Really? If you can tell the difference between ‑25°C and ‑20°C, you’ve spent too much time in North Dakota.

Back home, I was telling a friend about the trip. I mentioned that it was ‑25° on the mountain. I failed to include the temperature scale, and she actually asked, “Celsius or Fahrenheit?” All I could think was, “Does it matter?” It was cold! C-O-L-D!

International travel can be tough if you need to continually convert between temperature scales. Here’s an annotated Celsius thermometer with some benchmarks:

A related trivia question for which very few folks know the answer (without computing it): At what temperature does degrees Celsius equal degrees Fahrenheit?

February 7, 2011 at 7:56 am 3 comments

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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.

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