How can you use math to astonish your friends and family? Try the 21-card trick. Filmed for Numberphile, UC Davis Department of Mathematics Postdoc Anastasia Chavez demonstrates step-by-step how this trick works with the help of some simple math.

And if you like that one, try this slightly more complex 27 card variation, as demonstrated by mathematician Matt Parker:

After years of experiments, you’ve finally created the pets of the future – nano-rabbits! They’re tiny, they’re fuzzy ... and they multiply faster than the eye can see. But a rival lab has sabotaged you, threatening t...

Imagine trying to use words to describe every scene in a film, every note in a song, or every street in your town. Now imagine trying to do it using only the numbers 1 and 0. Every time you use the Internet to watch a...

Dutch artist Piet Mondrian’s abstract, rectangular paintings inspired mathematicians to create a two-fold challenge. Can you solve the puzzle and get to the lowest score possible?
Board game and puzzle designer and...

After months of travel, you’ve arrived at Duonia, home to the famous temple that’s the destination of your pilgrimage. The walk from the welcome center to the temple isn't a long one ... but there’s a problem. Can you...

Juggling legend Kris Kremo began juggling balls, hats, and cigar boxes onstage with his father Béla Kremo in 1970 at age 19, and joined The Blackpool Tower Circus as a solo performer five years later.
In this low-...

You’ve been chosen as a champion to represent your wizarding house in a deadly duel against two rival magic schools. Your opponents are a powerful sorcerer who wields a wand that can turn people into fish, and a power...

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 ...

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...

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...

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...

Search & enjoy 4,000+ smart & super-cool, “not-made-for-kids, but perfect for them” videos in the classroom or together at home, curated by Rion Nakaya with her 8 & 10 year olds. Click play and start a conversation.