Why I Let Students Use Calculators All The Time

“Sure! I’d  love to have you demo a lesson!” Ms. B’s eyes widened as a smile grew on her face. I was surprised and thankful that she was so open to the idea.

“Great!” I replied. “What unit are you doing right now?”

“Well, we just finished Quadratics and we’re about to start Volume and Surface Area.” Ms. B replied, pointing to the standards list on her wall.

“Okay, so how about I introduce Circumference and Area of circles?”

“That’s fine. What do you need for that?” Ms. B asked, ever eager to help.

“Do you have graph paper, calculators, rulers, that sort of thing?” I asked.

“Calculators? You let your students use calculators?” Ms. B countered, incredulous.

"You what?"

“You what?”

Yes, I do let my students use calculators.

Here’s why:

Lifelong Need

My wife doesn’t know her times tables. She’s a university professor and will regularly grade freshman Theology papers sitting on the couch. She’ll call out while I’m cooking or playing with the baby.

“What’s eight times six?”
“What’s 27 plus 18?”
“What’s 85 divided by 15?”

I'm a walking, smiling, calculator in the Vaudrey household.

Husband: a walking, smiling, calculator

When I’m not home, she has a calculator in her pocket all the time. Even if her phone is in the other room, she can Google it.

My wife doesn’t need computational skills.


…but she needs the reasoning.

She needs to know what the average means, when to find the sum of a row and give the total student points, and how to explain to her college freshmen what it means to have 6 quizzes, each worth 10% of their grade.

"But what if I miss one? Can I still get a C?"

“But what if I miss one? Can I still get a C?”

The students in Ms. B’s classroom also have calculators in their pockets. I want them to know how to use it effectively, which is a much better use of their time than memorizing their 12s tables.

Diane Kinch, former president of CMC and board member of TODOS, gave this truth bomb at a recent workshop:

Students have had 15 years to learn their times tables and they still don’t know them. At a certain point, I have to stop boring them, give them a calculator, and say “Let’s do some math”.

In my own classroom, we use TI-83+ calculators nearly every day, which I like for a few reasons:

  • TI-83s keep a record of the last 8 or 10 calculations, so if students clear accidentally, they can recall it.
  • There are tons of other buttons that do weird math stuff that we won’t use this year. This (f0r some) serves to build creativity about what’s coming next. About 2/3 of the students found the Stats Generator application and did coin-flipping trials four months before our unit on probability.
  • They could easily show their neighbor the order of steps and describe the reasoning that led them there.

Let’s work backwards


Students who focus on reasoning instead of computation are better prepared for college and career in the US.

(It’s notable that most of the grunt work for my CPA buddy’s tax clients comes from the western coast of peninsular India. Computation is a high value there.)

That’s why I use calculators in the classroom all the time; because I think that reasoning is more important than computation.

~Matt “Which one is the minus sign?” Vaudrey

Summer Update

I had a new baby.

IMG_4892 IMG_4902 IMG_4965


And still have this baby.


…so summer’s been pretty busy. I do have two things (in addition to that) to note.

1.) What a tragedy that Fawn Nguyen nearly lost hundreds of posts. If her content were lost, I imagine a herd of furious math teachers would’ve stormed the headquarters of GoDaddy.com and burned it to the ground. I’d hold a torch for that venture, too.

2.) My grandparents (who are 70+) live in Seattle and wanted to meet baby Clay. I walked Grammy through the installation of the Google Hangouts plugin and boom!

Screen Shot 2014-06-30 at 5.11.37 PM

Cross-country goo-goos and ga-gas.

My grandparents (who still use disposable cameras and balance checkbooks by hand) are open to new technology, and I hope that teachers in the coming year will be as receptive as they are.

~Matt “Close the window… it’s the red X” Vaudrey

P.S. If you want to follow the morning adventures of Pickle and Daddy (as Mommy and the new baby sleep in), you can follow me on Instagram.

Open Letter to Tom Torlakson, California Superintendent

Mr. Torlakson,

Good morning, you’ve no doubt heard that the existing tenure situation was ruled unconstitutional yesterday.

I myself was tearing up as I read the brief. For my entire career, I’ve felt what the court realized yesterday, and my relief and joy nearly made me weep during my meeting.

Mr. Torlakson, you’re currently “farther up” in the education chain of command than I–a lowly teacher–so it’s been a while since you’ve sat in a staff meeting or observed stinky teaching by a tenured “permanent” teacher.

It’s probably been even longer since you watched a stinky teacher make more money than you. For me, that memory is fresh.

Anyway, let’s talk about education.

In the court briefing:

“… teachers themselves do not want grossly ineffective colleagues in the classroom.” (page 13, line 1)

If I were in your position, posed for reelection, I would be tempted to please the California Teacher’s Association (one of my biggest supporters) in order to secure my seat in November.

I’m asking that you focus on the students instead. Our students deserve great teachers, and as State Superintendent, you’ll have the proper pull to drive the design of a system where great teaching is rewarded. This would help flush out the dummies and keep the hard-working professionals.

I hope you see that, by encouraging teachers to be our best, we place the students first.

In short, I’m a teacher, and my right to a job matters less than my students’ right to a quality education.

Mr. Torlakson, please support this court ruling in the next few months and continue to reform teacher tenure after your (probable) reelection in November.

~Matt Vaudrey

UPDATE June 25, 2014:

P.S. No doubt that by now, you’ve read the highly polarized brief from the CTA website, you’ve heard complaints that the “1-3% of teachers are grossly ineffective” statistic is unfounded on any data or studies, and you’ve seen that Students First is hailing the decision as an important step, with many more to address going forward.

Two things:

  1. As a classroom teacher, the “guesstimate” of 1-3% of all teachers are grossly ineffective is not only statistically likely, but it sounds pretty generous based on my anecdotal experience.
  2. The CTA press releases are full of negative language and the Students First releases are full of optimism and urgency. Why do you think that is?

Common Corgi: Mascot of Common Core

Marcia and I were discussing the need for a Common Core mascot this morning. She’s a dog person, so we came up with…

The Common Corgi.

Common Corgi - speak

Common Corgi - word problems

Common Corgi - cite

Common Corgi - effective tools

Common Corgi - independence

Common Corgi - investigate

Common Corgi - literacy

Submitted by Matt Enlow:

Common Corgi - staircase

Got an idea? Tell me about it:


~Matt “My Corgi Is Not Common” Vaudrey

Common Core Will Not Eat Your Babies

Let me tell you a story.

I’ve taught next door, across the building, and across campus from some really bad teachers.

unhelpful teacher

I have sat in staff meeting at the same table as teachers who give printed notes to students to copy down into their notebook, and that is their sole class activity for the year.

As a teacher, my profession is cheapened if bad teachers aren’t held accountable. That’s why we have standards; so that there is a minimum expectation to guide teachers and students.

I have a daughter (and a son on the way). In a few years when I send her to school, I expect the school to do a good job training her in skills she’ll need to be successful. Some things will come easily to her, some will be more difficult, and some will sit in darkness until a special teacher shines a light on them.

When I send my child to school, I’m giving my acceptance that school will do a good job. If I don’t like it, I can pull her out and home-school or private-school her.


Of course, your child isn’t common. No child is.

Schools do the best that we can with the diverse, unique students that are sent through our doors every day.

Therein lies my problem with the advocates against the Common Core;

If you don’t like it, you can leave.

Otherwise, you’re just the kid who goes to a birthday party and complains about the flavor of cake.

(Parents Against Chocolate Fudge)

(Concerned Parents Against Chocolate Fudge)

~Matt “Not afraid of Common Core, but a little afraid of the trolls this post will attract” Vaudrey

Chalk Art for Math Daddies

My daughter has water-soluble sidewalk chalk and free reign of the backyard.

Here’s the thing though: As adults, we rarely have to go outside our comfort zone. I don’t draw much. Most of my adult life, the drawings I’ve done are geometric figures.

So I’ve been mixing things Pickle wants me to draw with the things I can draw well. She asks for something, and I add to it.

A dinosaur chasing a square root function.

A dinosaur chasing a square root function.

A black sheep standing on convex polygons.

A black sheep standing on convex polygons.

Snakes on a plane. Get it?

Snakes on a plane. Get it?

An owl and a banana circumscribed by an isosceles triangle.

An owl and a banana enclosed in an isosceles triangle.

A robot with a RAY gun. See it? RAY?

A robot with a striped face and a RAY gun. See it? RAY?

A blue sheep walking on a rhombus.

A blue sheep walking on a rhombus.

The locus of points equidistant from a baby.

The locus of points equidistant from a baby.

...and tangent to a green bee.

…and tangent to a turquoise bee.

A linear function tangent to two sheep and a cat bounded by a negative parabola.

A linear function tangent to two sheep and a blue stick-cat bounded by a negative parabola.

My kid is gonna blow the socks off her math teacher.

~Matt “Daddy coloh lello seep?” Vaudrey

Big Shark

In the last few months, John Stevens and I have been training teachers on Math and Technology in the classroom with La Cucina Matematica.

Things are good.

One of the lessons in La Cucina hasn’t been recorded here yet, so here we go.

Big Shark

Start class with the media, which I got from Timon Piccini.


All students: Whoaaaaa!

Here’s why this is an excellent 3-Act math task:
Students immediately start asking questions.

Alex: How tall is that lady?
Marie: Is that shark still alive?
Dylan: What’s her Mullet Ratio?
Mr. Vaudrey: Aw, you’re a sweetheart. What else?
Lorraine: Do any other organisms live in a symbiotic relationship with it?
Mr. Vaudrey: Wow. Ms Smith owes you a high-five for that one. What else?
Victor: Is that one shark or two jaws facing each other?
Alyssa: Is she standing, like, really far back to make it look bigger?
Luis: What does that shark eat?
Frankie: Is that a Megalodon?

To that question, I responded, “I dunno. What’s a Megalodon?”

Frankie then had the full attention of the class as he stood and described the giant prehistoric shark that is large enough to destroy boats and battle a giant octopus. He was crushed to find out that the Megalodon is actually extinct and has never been captured on film.

“But!” I say, borrowing Frankie’s excitement and pausing dramatically, “Scientists noticed a lot of similarity between this:”


“and … this:”


“What’s happening here?” I ask.

Frankie (now very helpful): That guy is holding a shark jaw.
Kamiah: Is that a Great White shark?
Mr. Vaudrey: No, that’s a man from south Florida named Barry… Oh, you meant the jaw he’s holding. Yes, the jaw of the Great White is like a smaller version of the Megalodon. Do you see the similarities?

(Go back and forth between the two pictures as students nod).

How do you think those two sharks are related?

Tionne: Well, like what if the Megalodon was… like… the ancestor… of the Great White?
Luis: No, it’s not. This one is way smaller.
Tionne: Yeah, it is! Look at dinosaurs and like… lizards and stuff!
Mr. Vaudrey: You’re both right. The Megalodon is related to the Great White shark, but the Great White is way smaller. Does anybody disagree?

Scientists noticed what Tionne noticed; that the jaws are similar and the Megalodon was probably related to the Great White shark that we have today. Here’s the thing, though: The skeleton of a shark isn’t bone, it’s cartilage. So we don’t actually have a full skeleton of the Megalodon and don’t know how long it is. Scientists noticed this, though:


The teeth are almost identical, except for the size. They also noticed that the bigger the Great White, the bigger the jaw.

[Lead students through discussion about proportional relationships until...]

Dream Student: So if we compare the teeth, we can figure out the length? 1
Vaudrey: What luck! We happen to have such a format on page 68! Go there.

Megalodon Notes blank

Fanda: Wait, how long is the Great White?
Vaudrey: Oh, yeah. Here.


Teacher Notes:

Depending on the class, you can go through unit conversion, take guesses first, whatever. I followed the flow of the class; if they had concerns about the units, we converted feet to inches or mm or whatever. If they didn’t care, then I just made sure the end result was in feet and they could explain how they knew.

megalodon notes

The numbers in black on the right side were technically the “answer”, but didn’t quite have the catharsis that we wanted. So we went outside.

Students took 20 paces from the blacktop, which varied “much like the size of a shark would have varied between 56 and 64 feet.

Turn around and look back at the blacktop.”


Vaudrey: The distance from you to the blacktop is the about length of a Megalodon.
Alan: Holy shit!

This is one of a few lessons that got students excited enough to yell “Holy shit!” at the end.

Then we went back inside and I showed them this:



and this:


Maria: I wonder how tall the fin is.
Fernando: Could the big shark swallow a bus?
Ramiro: How many humans could it eat at once?
Vaudrey: Let’s get into those questions tomorrow.


All the downloads are here.

And click here to email me and book La Cucina Matematica for your district, school, or county.

~Matt “Big Shark” Vaudrey



1. I teach RSP, it’s unlikely that they would jump here so quickly. An actual 2nd period would involve turning to yesterday’s page in the notebook and looking for similarities.