Category: Math Around Us

Math Holiday Shopping Day
There’s a lot of math involved in shopping. And around the holidays, since there’s a lot more shopping, there’s a lot more math.

Today is special.

Today is Sibling Christmas Shopping Day. An unofficial holiday created by my mother’s children a few years ago. My three siblings and I head out to the mall. Just us. No children, no spouses.

We act like a bunch of wild 10 year olds stuck in grown-up bodies. And we’re not small grown-ups.

If you’re in Memorial City Mall today, look out.

There’s math in Sibling Christmas Shopping Day.

There are three sisters and one brother. All of us wear clothing and accessories according to traditional gender roles. So how many Christmas earring ornaments do we need?

And who will bring them?!

There are four of us, and we’re shopping for each other. In how many different ways can we group together in pairs of two to optimize shopping for each other?

And how on earth will we make sure to stay hidden!?

My Christmas shopping budget for the day is $200. I have seven people to buy for and want to spend roughly the same on each one. I also want to buy coffee at Starbucks, lunch, and take some picture booth pictures. What’s a good estimate for me to spend on each of my seven people?

And why can’t I have a bigger budget? *sigh*

The probability for us getting thrown out of a store for horsing around is .04. There are about 200 stores in Memorial City Mall. If we visit 150 stores, how many times will we be kicked out for horsing around?

And how can I make sure to blame it on them?

We’re meeting at 9:30 and wanting to get done around 3:30. If we each have seven people on our lists, how many presents should we buy each hour to make sure we get everything done?

And who’s going to be late to mess up all the math we’ve done figuring this out?

If the line to see Santa is 45 minutes long and we all want to crowd on that poor man’s lap together, when should we arrive to do this so that we don’t take away any shopping time?

And who’ll be the lonely sib stuck in line holding our place until the others finally show up?

Math Fun, Mall Fun

When you take your children shopping this season, start your day with a budgeting conversation. Even if the sky’s the limit you can visit about how much each child wants to spend. Revisit the topic at the end of the day and discuss their impressions of the value of things – were items more or less expensive than they’d anticipated? Did they go over budget?

During the shopping trip, point out places where there are discounts. Discuss “just-for-you” deals that the kiosk clerks offer. Consider real value and how it compares with perceived value.

Look around for ways to count, talk about time or money and look for patterns. When you do, point it out and say, “and that’s math!”

And share what you see!

Leave a comment below if you find anything interesting. And if you see a bunch of grownups acting worse than any kid you’ve seen… well, it’s not me. Really.

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December 5, 2011
Math Songs
I’ve been wanting to write about all the cool math songs out there for quite some time. I’ve been somewhat collecting them in hopes that I’ll have the world’s biggest collection of math songs.

Alas, I’m fairly confident that I’ve only managed to round up about 10%. They range in educational value, music quality and catchiness. Songs that I love, Daughter isn’t quite interested in. The one she loves I sometimes find slightly boring (especially after 3,000 times of replay).

Not all math songs are good.

Math and music are very similar in that everybody has their preference. I’m not a fan of calculus. And I’m not a fan of rap music. (Not that calculus is the mathematical equivalent of rap music, but for me it’s just as annoying.)

If you’re searching for math songs, make sure you give them a listen before you buy. There’s a lot of garbage out there (sometimes that’s an opinion and sometimes that’s a technical fact).

There’s also some NSFW stuff too – which can be fun for grownups, but you don’t want to inadvertently play something nasty for your parrot two year old (I’m speaking from experience here, #jussaying).

Here’s my collection of songs and albums.
- Do The Math by Ralph’s World is a song about friends… who happen to be shapes: Sanderson the Square, Tony the Triangle, Poly the polyhedron (non-Euclidean) mass. So fun!
- Schoolhouse Rock: Multiplication Rock – the best ever. I’ve been singing this to Daughter since she was born! “Three is a Magic Number” still makes me tear up.
- The Math Song by Scott Perry – I just downloaded this off iTunes and I’m excited about listening to it – over and over!
- Another I grabbed this morning is I, Pythagoras (The Math Song) by Nikki Shultz. This is more of a grown up song, but she’s got an amazing voice.
You can even make your own!

Like I did (and had Husband sing it) with The 1-2-3 Song.

Or have your students do it! This song was recorded about ten years ago for me by Sidney & Dale, two Art Institute students in my Fundamentals of Math class:

So how about it – what math song is your favorite? And what math song would you like to hear, sing or write? Share it in the comments (and include a link to the audio or YouTube video).

Sing the news loud and click here to share this on Twitter/X.

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November 30, 2011
Introducing Count 10 Read 10
Count 10 Read 10 is a family numeracy and literacy initiative. Read more about it on the Count 10 Read 10 page and watch this video explaining all about it:

Tell all your followers about Count 10 Read 10! on Twitter

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November 17, 2011
Mathematicians are People Too – And They Make Mistakes!
This story is in honor of my best friend’s 41st birthday. She’s called me “Michelle,” my middle name, since we met in 1977. Happy Birthday, Tammy!

Two friends, Tammy, a poli-sci major, and Michelle a math major, were carpooling home from college one day.

While on the freeway, Michelle recalled an interesting fact that she had recently learned.

“Did you know the interstate freeways that run east and west are all odd numbers, and freeways that run north and south are all even numbers?”

Tammy began to think.

“Like I10 runs east and west and it’s an odd number,” explained Michelle.

Tammy was silent.

Minutes passed.

Tammy finally said, hesitantly, “Michelle, I know you’re supposed to be the math person here, but I’m pretty sure that 10 is an even number.”

Michelle replied, “Oh, yeah, I meant the other way.”

The moral: Be confident. Even if you’re wrong.

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October 23, 2011
Wordless Wednesday: Fibonacci Baskets
I rarely do Wordless Wednesday, but some photos just lend themselves to it!

These are from IKEA.

In case you’ve not yet taught the Fibonacci Sequence, it starts with 1, 1 and then each next number is the sum of the previous two numbers:
- Next is 1 + 1 = 2
- Then 1 + 2 = 3
- Then 2 +3 = 5, etc.
How about some questions…
- How many sets do I need for the next number? (A set from Ikea has 1, 2, and 3 in it.)
- How many sets do I need for each number after that?
- Is there a pattern? Like for the 12th number I need 12-2=10 sets and for the 17th number I need 17-2=15 sets?
Do you have more questions? Or answers? Share in the comments.

(150 words later my headline is pretty much wrong, huh?)

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October 12, 2011
What is “Living Math”?
Look – there’s a 30 degree angle!

Some folks over at the Living Math Forum were wondering if they were doing living math right.

There’s probably a fancy definition of living math, but I don’t know it.

The fact is that we all live math! The trick for parents and teachers is to point it out to our kids.

Ever sat waiting in a doctor’s office with a child? You find yourself “edutaining” them with, “Look, the chair is BLUE!”

Remember to also say things like, “Look, there are five chairs and six people…”.

Encourage them to notice that one lady is sitting on the floor because there aren’t enough chairs. Voila! Subtraction!

So counting people is living math. As is going grocery shopping, cooking, drinking 1/2 cup water, and breathing 87% O₂.

You’re doing it right because you just can’t do it wrong!

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October 9, 2011
Memorizing Parent Phone Numbers Is Math and Safety!

I’m a math mom. And I’m a paranoid mom. So when I saw the opportunity to put these two together on a daily basis, I was elated.

Every night before bed we say our “words” right before our prayers. The routine sounds like this:

My name is Doodle Crowder. My dad’s name is Big Crowder.* His number is 713-555-1254. My mom’s name is Bon Crowder. Her number is 713-555-1245. Thank you Jesus for letting me have a good day. Be with everybody who loves me, including…

The safety benefit is obvious.

If she’s ever lost or otherwise not where she’s supposed to be – at any age – she’ll have our phone numbers ingrained into her little noodle. With that memorized so clearly she’ll be able to tell any police officer around exactly to whom she belongs.

This makes me much more comfortable about her growing up.

The math part is really cool.

We teach children this poem:

One two three four five

Six seven eight nine ten

But this really means nothing. They’re just words. Until a child can associate each word with another (different) object, “counting” is merely a trick.

Kind of like thinking that a kid can read just because they know how to sing the alphabet.

And the association of each number word with an object is really very advanced. Especially since “seven” has two syllables. Might “se” and “ven” each be a number? And there’s no telling (for a child) if “won,” “wonto” or maybe “wontothree” is a single number!

Kids differentiate number words by hearing other combinations!

If they hear “towonthree” and “threetowon” and “wontothree” they can start to see where the sounds break. If “se” and “ven” are always stuck together, they start to understand that “seven” is a single word.

Phone numbers are a great way to help them say and hear lots of number words in different orders. And it keeps it from getting too boring for you.

Safety and math go together!

So add the phone number routine to the front of your prayers. Pick the top two or three phone numbers in your little one’s lives and say them every night.

And share your thoughts on this. What else do you do in your bedtime routine that supports math?

*Names changed to protect our privacy – whatever little sliver of it there might be left. 😉

September 26, 2011
A Human Interest Story Involving Math: The $100 Battery Charger
My day job colleague told a beautiful story yesterday. He had been washing his car late at night, in the dark, and was approached for assistance. He is generous beyond belief, and apparently he made a real impact.

Oh, and it involved a little math.

I was washing my car the other night and really getting after it. I had the scrubbing brush going and was really making progress on getting the car clean. I was totally focused and I felt a tap on my shoulder. It startled me and I turned around to be faced with a large African-American woman who said, “I’m sorry, I don’t mean to interrupt, but we’re having car problems. Is it possible you can help us? I think we need the battery jumped.”

I looked down the street and saw no other people and no car. Within a split second I remembered my latest purchase: a wireless battery charger that needs no people, no cables and no extra car to jump a battery. I got it out of my garage and handed it to her.

“I’m in the middle of washing my car. Why don’t you borrow this? It should help.”

She thanked me and walked away with the charger. I got back to washing my car.

Five minutes later there was another tap on my shoulder. Another African American woman was standing there holding a five dollar bill. She offered it to me.

“Oh my goodness, no,” I said. “I’m not taking your money. I’m just glad I could help.”

Another 5 minutes went by and I saw one of the ladies put the battery charger close to my garage. I was really getting into the car washing at this point – suds everywhere – so I didn’t pay much attention.

When I was returning my carwash supplies to the garage, I saw a crisp new $100 bill on top of the battery charger!

That thing was only $40 – and they just gave me $100 to borrow it!

This is a wonderful and touching story. These ladies were having difficulty finding someone to help them. Not only did my friend help, he also freely gave them something to use and trusted without question that they would return it.

They, too, were moved by his generosity.

The numbers don’t work.

It looks like this:
- Battery charger cost: $40
- “Rental fees” offered: $5
- Shown gratitude: $100
The numbers don’t make sense. And in a way they shouldn’t. The $100 bill wasn’t really money. It was the biggest, fattest, loudest thank you note ever written. There’s no value you can place on someone being free and generous and trusting.

It still goes in as $100 in the eyes of the bank. But what do they know?

Notice the math and share the story.

When you share this story, point out the math. Especially if you tell this in front of (or to) children. Making the connection of generosity and emotion to math will help everyone see how integral math is in our lives.

How about you? Do you have a story of generosity that you’re just now realizing involves math? Share it in the comments!

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September 22, 2011
The Math in Credit Card Security
We had a fun little discussion via email at the day-job. Someone changed the code on the combination lock and the discussion around combinations, permutations, cryptography and all things sneaky-math cranked up.

It reminded me of this neat fact I learned about credit card security.

Not all digits on a credit card are created equally!

A credit card is made up of 16 numbers. But only the first 15 are “random,” according to NRich Math. The last number – the 16th number – is the “check digit.” It’s calculated using a fancy formula using the first 15 digits.

This check digit helps a computer system quickly determine if a credit card number is fake. Now, it can’t confirm that it’s real – it just can help determine if it is fake.

The digit is created using a method called Codabar.

First, let’s define some things.

An odd digit is a digit in the credit card number that is in an odd position. For the photo of the card here, the number is: 5184 8204 5526 6423:

The odd digits are 5, 8, 8, 0, 5, 2, 6, 2

An even digit is a digit in the credit card number that is in an even position. For the photo of the card here, even digits are 1, 4, 2, 4, 5, 6, 4, 3

The check digit is the last digit – it gets calculated and isn’t considered in either odd or even position. It’s a super special digit.

The method is weird – and kinda fun!

Here’s what you do:
1. Add up all the odd digits, or the digits in the odd positions: 5 + 8 + 8 + 0 + 5 + 2 + 6 + 2 = 36
2. Double that number: 36 × 2 = 72. Save this number, 72, for later…
3. Add the even digits together, or the digits in the even positions: 1 + 4 + 2 + 4 + 5 + 6 + 4 + 3 = 29. Save this number, 29, for later…
4. (This is a freaky step.) Count the number of odd digits that are greater than 4. The odd digits are 5, 8, 8, 0, 5, 2, 6, 2. Of these, 5, 8, 8, 5 and 6 are bigger than 4. There are 5 of those total. Save this number, 5, for this next step…
5. Add up the results you saved from steps #2, #3 and #4. 72 + 29 + 5 = 106
6. Take the answer from step #5 and figure out how many you need to add to get it to the next multiple of 10 (or the next number that ends in zero). The number after 106 that ends in zero is 110. So we need to add 4. 106 + 4 = 110. 4 is the super important number.
7. That final super important number – well, that’s the check digit! That’s the last number that should be on the credit card – if it were a real card!
For the picture, the check digit should be a 4. And it’s a 3. So I can tell instantly that this is a fake credit card number.

You can use this to teach your children!

Stuck in a waiting room with a 10-year-old? All you need is a pen, piece of paper and any credit card in your wallet.

Teach them the method and have them check all of your credit cards. Or tell them you can guess the last digit of any credit card number.

Either way, you’ve got an instant source of entertainment wrapped in a ball of education!

What do you think? Are you racing to your purse right now to check your cards? Share your thoughts in the comments.

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September 15, 2011
Back to School Math Clothes
For many across the world, today is the first day of school. For after schooling families, or blended homeschoolers going to a co-op, you’ve probably been shopping for new clothes for a few weeks. For those in areas that offer tax-free back-to-school weekends, you no doubt have taken advantage of that. Even if you unschool on a sailboat hopping around the coast!*

And why should the children have all the fun? Why not do a little back-to-school shopping of your own?

And of course, don’t just buy any clothes, buy math clothes!

Math accessories dress up a business or formal look.

At a fancy business meeting, or a full tilt gala, show your affinity for math with your jewelry. This Fibonacci sequence necklace is a beautiful addition to the little black dress or business suit:

Notice the Fibonacci sequence: 1, 1, 2, 3, 5

This artist is working with me to create some really neat Fibonacci earrings and matching bracelet. We’re also working on other patterns and concepts for jewelry that says, “Math is cool, and it’s pretty too!”

Business casual means t-shirt with a blazer.

My favorite outfit is a math T-shirt with a blazer over the top. I wear some slacks and modest heels and I’m ready to take on the world. Here’s a T-shirt that I found that’s on its way to me now:

This “obtuse” shirt is created by Matt at ExBoyfriend Collection (now BoredWalk), who is generous enough to give one to me! I’ll post a photo in full dress when it arrives.

It reminds me of what my Ma used to tell us: “Quit being so obtuse!”

Matt creates other math t-shirts too! We’re looking at collaborating on some – so keep your eyes peeled.

Take it to the limit with casual wear.

You can also wear a t-shirt as just a t-shirt, with shorts or capri pants.

This infinity shirt is from Mike who publishes MathFail, Spiked Math Comics and Math Shirts.

What’s your favorite math outfit? Are you hitting the stores for yourself this back-to-school season? Share with us in the comments!

* BTW, that’s my homeschooling dream – on a sailboat, unschooling around the coast!

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September 6, 2011