RANDOM ACTS OF MATHEMATICAL DELIGHT

Use these teacher-recommended mathematical gems at random moments in your classroom.

Here’s a collection of videos recommended by colleagues across the globe.

Some pieces are short and make for excellent classroom starters. Some are longer for the odd ten- or fifteen- moments of class time. Some are longer still for full class activity.

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Today's Featured Video

Today's Featured Video

Do you know your personal polynomial?

Do you want to see a mathematical formula spells your name? Do you want to see a graph of your formula?

Check out this cool app that shows you your name in math!

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Equations

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The Citardauq Formula

A strange way to solve quadratic equations

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Lill’s Method

Solving Equations by Shooting Turtles with Lasers

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Find your PERSONAL POLYNOMIAL

Here’s how to find a formula that fits any set of data

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Completing the Square

Eddie Woo, winner of Australia’s Local Hero Award, selected this fabulous video. He says, “For a literal sense of ‘mathematical delight,’ it’s definitely worth spending the four minutes to watch this all the way through — listen to the sound of my students reacting when the penny drops. It’s priceless!”

Geometry

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Infinite Cake Anyone?

How is it that I seem to be generating infinite amounts of cake?

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A Cute Paper Trick

Can you figure out what is going on?

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Why Does Slicing a Cone Give an Ellipse?

Grant Sanderson (3Blue1Brown) selected this lovely video for GMP noting, “This should only involve elementary geometry and captures a really delightful piece of mathematical cleverness.”

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Unexpected Shapes

Playing with Moebius bands... and beyond!

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Alles is Wiskunde!

Playing with modular origami.

Math Salute

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The International Math Salute

James Tanton teaches James Grime the salute

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The Salute in Tanzania

Experience exuberant joy!

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The Salute Explained

James gives away the details

Numbers

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How High can you Count on Your Fingers?

The answer might surprise you

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A Square Root of Two cartoon from BEN ORLIN (introduced by James).

The inimitable Ben Orlin selected this gem of a cartoon for us to share. He had this to say about it : “Irrational numbers are bottomlessly weird. Sometimes I think I’ve gotten used to their strangeness, and I like it when a thought experiment like this one (delivering mail to the square root of 2) can shake me out of my complacency and remind me again of how unfathomable they are.”

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Frogs and Buns

What’s a good way to share buns?

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Dots & Tods from GMP; Piles & Holes from MINDSETS

Go from this teaser to the full experience: www.mindsets.com/global-math-project

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The Golden Ratio

Why is it so irrational?

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A Pythagorean Number Puzzle

A curious puzzle that unites Pythagorean triangles with a numbers game.

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A Crazy 6s Puzzle

There is too much structure here to be coincidence!

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How to Multiply Without Multiplying

A ancient way to compute products

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Line Multiplication

Can you figure out why this curious method works?

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Powers of Ten

A classic video giving an intuitive sense of scale.

Miscellaneous

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How to Split Things into Thirds

From folding to sharing

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Hexaflexagons

The incredible Vi Hart selected this video from among her many wonderful offerings noting, “Hexaflexagons is by far my most popular!”

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More Videos to Come

Probability and Expected Values

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A Gender Balance Puzzle

Here's a puzzle alleged to be an interview question at high-tech companies.

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The Surprising Math of Twinkle Twinkle Little Star

A curious word-counting phenomenon

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What is the Best Way to Win at Monopoly?

Tom Rocks Maths selected this lovely video for GMW. It demonstrates how a simple understanding of probability can be used for almost anything, including devising a winning strategy for everyone’s favorite family board game!

Riddles

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The Cuddle Duddly Fuddly Wuddly Riddle

Stop the video before the puzzle is solved

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The Giant Cat Army Riddle

Stop the video before the puzzle is solved

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The Unstoppable Blob Riddle

Stop the video before the puzzle is solved

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The Wizard Standoff Riddle

Stop the video before the puzzle is solved

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The Time Travel Riddle

Stop the video before the puzzle is solved

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The Rogue AI Riddle

Stop the video before the puzzle is solved

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The Penniless Pilgrim Riddle

Stop the video before the puzzle is solved

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The Vampire Hunter Riddle

Stop the video before the puzzle is solved

Pi

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Calculating Pi with Real Pies

Matt Parker selected this video for us (created in collaboration with Brady Haran), noting, “This video is hands-on fun with mathematics and encourages anyone to have a go at finding their own ridiculous way to estimate pi.”

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Pi for a Square

An old video but a goodie!

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A Mile of Pi

Brady Haran, the brilliant master of @numberphile, selected this video of Matt Parker's. Brady said, “[This video] seemed like impossible dreams. How could we print out 1 million digits of Pi on a continuous piece of paper? Turns out there was a place in Denmark that could help. Where could we possibly roll out a mile-long piece of paper? Turns out there was a runway we could hire. Where could we get hundreds and hundreds of pies to make into a big Pi demonstration? Turns out a friend of mine worked in a pie factory! I love these videos because they were silly ideas that somehow came true — and they resulted in memorable demonstrations of why we’re all so captivated by Pi.”