# Math Ideas

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### Card Table Proof of the Pythagorean Theorem

We own a standard card table that we leave tucked away in the basement until the kids want to have a lemonade stand on the front sidewalk or we need …

Mathematics### High School Geometry Guide: semester 1

Geometry Semester 1 Organized by Lisa Bejarano: @lisabej_manitou<p>Unit 1: Constructions & Rigid Transformations<p>CCSS<p>1.1 I Know and use precise …

### [Desmos Design] Why We’re Suspicious of Immediate Feedback

One of our design principles at Desmos is to “delay feedback for reflection, especially during concept development activities.” This makes us weird, …

Mathematics### Would You Rather...?

Latest Posts<p>Would You Rather buy the candy on the left or the candy on the right? Whichever option you choose, justify your reasoning with …

### Using Paper Folding to Introduce the Notion of Proof

Two years ago, I worked as part-time geometry instructor in a technical school near our university. Most of the students in that school were quite …

### Returning to Patty Paper Geometry

I had a busy week at work last week and didn’t plan ahead for today’s Family Math. Luckily we’ve got plenty of math books laying around and the boys …

Mathematics### How to Quickly Access Ten Google Sheets Templates for Teachers

Flippity is a great resource for G Suite users that I have been sharing with readers for a couple of years now. Flippity provides teachers with handy …

### Square Dance

<b>I recently debriefed with a fellow (teacher I support) about two activities</b> focusing on Squares, Square Roots, and Irrational numbers. Let's build …

### Converse, Inverse, Contrapostive Exploration

Converse, Inverse, Contrapostive Activity from Sam Shah and PCMI<p>I wanted to introduce Converse, Inverse, and Contrapositive in a way that had …

### Entrapment: Transformation Math Games

This visually challenging game helps students understand congruence through translation (slides), rotations (turns), or reflections (flips). At the …

Mathematics### Snowflake Tessellation Art

Previously, I had created a snowflake design with draggable points using Desmos (click on image to interact with it using Desmos):<p>My 3 year-old …

### Online coding lessons that teach you about math.

There's a lot here. If you login we'll track your progress.<p>Code with Google Charts<p>171 total lessons.

### 5x5 Most Amazing Just for Fun Game

<b>I call this game 5×5</b> (or 5 by 5). You use a sheet of 5×5 grids to play this game. Here is the game board I give students.5×5 game You will have time …

### Quadrilaterals: Coordinate Proofs & Facebook Projects

I’ve been teaching a unit on ‘quadrilaterals’, which I would describe as investigating the relationships between the different types of …

### Solving for Xmas: how to make mathematical Christmas cards

With less than a month to go before Christmas Day, it’s time to start thinking about cards. Here Oxford maths don Vicky Neale explains how to impress your friends with these stunning geometrical designs. It’s Christ-maths time, and there’s no need to be afraid.<p>Christmas is a fantastic opportunity …

Christmas### Intro to Conics with Rice Krispies!

My colleague uses play-dough to explore conics. And that was what I had planned to do until I read in Twitter one day that Julie was making rice …

### World Record Distance for Throwing a Fish at a Stop Sign

What is the world record distance for throwing a fish at a stop sign? Hey, I don't think this stuff up. But one of my students did. Try to imagine a …

### The Mathematical Surprises of Triangles, Squares and Pentagons

There are 101 non-fiction, and several fiction, books credited to popular science and mathematics writer Martin Gardner (1914-2010) , who would have …

Mathematics### Evolution of a Theorem (or How to Save All the Animals)

It all started when Bowman Dickson posted The Dead Puppy Theorem and Its Corollaries. Others joined in on the effort, most notably the additional …

Mathematics### Jump in the online math teaching community!

A number of years ago, I had the idea of starting a little program to help those interested in starting a blog do so. And we’ve had some fun …

Mathematics### MTBoS

I've been wanting something like this for a long time, but finally got around to making it. This is a search engine that only combs through Math …

Twitter### I can’t believe I didn’t realize you could think of subtracting negatives like this

A week ago, I thought I knew all the ways that kids could and would think about subtracting negatives. Then this happened and my world is a brighter …

Owe### The Evolution of My "Post It! PROVE It!" Idea

First of all it is so nice to have time to sit down and write a blog post.... :o) Time has been my enemy lately...<p>Wow.... I can't believe the 1st …

### Stuff Worth Sharing: Mathematical Clipart

Today I'm super excited to share with you my favorite source for mathematical clip art. This is one of those websites that I assume that everyone …

### Day 11 – Transformations on Desmos

The students were instructed to go to this link and match up as many parabolas as they could using the sliders a,b,c, and d. After playing around …

Texas Instruments### Teach Math with Spiralled 3-Act Tasks – a full course

This semester was my first go at spiralling a course through problems instead of units. Traditionally we teachers follow the chapters and sections …

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