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# Topic: *math*

## How Notes and Beats Go Together (The Rhythm Pyramid) – Classical MPR

How do musicians know what notes to play and for how long each note lasts? How do the notes and beats mix to make music? From Classical Minnesota Public Radio‘s Class Notes series, learn about note duration and rhythm...

## The infinite life of pi

The ratio of a circle's circumference to its diameter is always the same: 3.14159... and on and on (literally!) forever. This irrational number, pi, has an infinite number of digits, so we'll never figure out its exac...

## How To Make a Hexaflexagon: The Definitive Guide

How do you make a hexaflexagon in under a minute from any long scrap of paper without scissors, tape, or glue? 'Mathemusician' Vi Hart is well-known for her love of hexaflexagons, hexagonal flat paper models that can ...

## The Sound of Ice: Skating on thin black ice makes sci-fi movie laser sounds

This small lake outside Stockholm, Sweden, emits otherworldly sounds as Mårten Ajne skates over its precariously thin, black ice. “Wild ice skating,” or “Nordic skating,” is both an art and a science. A skater seeks o...

## Universal Calendar Puzzle: Figure out the day of the week for any date ever

Learn how to calculate the day of the week for any date you can think of with this impressive mental trick and some practice. In this It's Okay to Be Smart video, Universal Calendar Puzzle, Joe Hanson demonstrates the...

## How to multiply numbers by drawing lines

Learn how drawing lines and counting can visually calculate multi-digit multiplication problems. This handy math trick, sometimes referred to as the Japanese Multiplication Trick, lets little kids, visual learners, an...

## An unexpected way to inflate a balloon – Numberphile

The kamifusen is a traditional Japanese paper (kami) balloon (fusen) toy that became popular in the 1890s and can still be found in a variety of designs or decorated as spherical koi, pufferfish, penguins, monkeys, ra...

## The mighty mathematics of the lever

Archimedes once said “Give me a place to stand, and I shall move the Earth.” While the idea of a person moving such a huge mass on their own might sound impossible, chances are you’ve seen this idea in action at your ...

## How to equally share a cake between three people

When sharing cake between two people, the envy-free recommendation is for one person to cut the cake, making the two pieces as equal as possible, while the other person picks their preferred piece. With this agreement...

## Ballet Rotoscope

A ballerina dances as the joints on her body are traced with a computer-generated rotoscope animation technique, an algorithm that brings a mathematical layer to her natural movements. Ballet Rotoscope (2011) was crea...

## How many ways are there to prove the Pythagorean theorem?

What do Euclid, 12-year-old Einstein, and American President James Garfield have in common? They all came up with elegant proofs for the famous Pythagorean theorem, one of the most fundamental rules of geometry and th...

## The Kresling-Pattern and our origami world

Biruta Kresling is a Paris-based architect and independant researcher on folded structures—specifically how nature folds and unfolds tree leaves, tortoise shell bamboo, turbinate mollusk shells, the air sac of the h...

## Three Gears are Possible

If you've ever seen an image of three gears all interlocking or an odd number of interconnecting gears, like those gears on some British two pound (£2) coins, you've seen a gear configuration that does not work. Howev...

## Can you solve the fish riddle?

As the cargo director on the maiden voyage of the S.S. Buoyant, you’ve agreed to transport several tanks containing the last specimens of an endangered fish species to their new aquarium. Unfortunately, the boat is ba...

## A 3D printed mechanical laser show machine

Engineer, maker, and 3D printing enthusiast Evan Stanford has created a 3D printed, hand-cranked mechanical laser show machine that 'draws' with projected light. The drawn shapes are created with two rotating cams tha...

## Turing Tumble, a DIY mechanical computer powered by marbles

The Turing Tumble, this small Pachinko-like puzzle game prototype, is also DIY mechanical computer. Programmer Paul Boswell designed the Turing complete toy to help kids (and adults) learn, see, and feel how computers...

## The Universal Tea Machine, a huge mechanical ‘adding computer’

"The better your binary addition skills the better your cup of tea!" The Universal Tea Machine by Smout Allen is a huge mechanical 'adding computer' that mixes tea and mixes tea, a British tradition that became popula...