# Math

No calculators allowed! This is a pretty fun one to work out. Thanks to all patrons! Special thanks to: Ertugrul Oruç, Michael Anvari, Richard Ohnemus, Shrihari …

42 was the last remaining number below 100 which could not be expressed as the sum of three cubes (*) – UNTIL NOW More links & stuff in full description …

Many tests around the world include a problem like this. How can you calculate this quickly, without making any mistakes? Thanks to all patrons! Special thanks …

Second of three videos we’re doing on Navier Stokes and related fluid stuff… featuring Tom Crawford. More links & stuff in full description below ↓↓↓ See the …

A dog, cat, and mouse run around a triangle at different speeds. Can you figure out angle ABC? It seems impossible but the answer works out magically! Thanks …

Tom Crawford (sporting a Navier-Stokes tattoo) talks about the famed equations – subject of a $1m Millennium Prize. More links & stuff in full description below …

Where did the extra money come from? Learn the answer to the problem stumping people around the world! Subscribe: …

Oxford ranks as one of the top universities in the world. Learn how to solve this coin flipping game, which is adapted from an actual interview question! The video …

Featuring Neil Sloane from the OEIS. Full “Amazing Graphs Trilogy” and extras at: …

Can you estimate the log of 3 to the base of 2 without using a calculator? This kind of skill is actually pretty important in university mathematics. Watch the video …

A triangle with sides of 4, 3, and 5 is drawn inside a square as shown. What is the length of the square’s side? It’s a fun little geometry problem! Sources …

See Amazing Graphs Part 1 at: https://youtu.be/pAMgUB51XZA Check out Brilliant (get 20% off their premium service): https://brilliant.org/numberphile (sponsor) …

This is adapted from the GRE, an American test often required for graduate school. You have about 2 minutes to solve each math question. Source …

It may not be exactly 99 percent, but many people will get the incorrect answer. It’s a great teaching opportunity. Learn how to solve this problem! (There are …

Featuring Neil Sloane of OEIS fame. Even more unexpected graphs in our next video. More links & stuff in full description below ↓↓↓ More Neil Sloane videos: …

A surprising link discussed by Professor Sergei Tabachnikov. Extra footage at: https://youtu.be/MJ1NAzpens4 More links & stuff in full description below …

Olympiad problems are challenging for most of us. But this one was considered “easy” for the students taking the test! (The oldest students are in high school, but …

What is 8÷2(2+2) = ? Everyone is arguing about this problem, so let’s figure out the correct answer! The problem involves the order of operations, historical math …

What is the distance between towns A and B? Learn how to solve this mysterious problem–a similar problem was a question to quality for the US Math Olympiad …

This is a fun puzzle to celebrate the 50th anniversary of landing on the moon! Source @NASASTEM on Twitter …

This is adapted from a problem given to 14-16 year old students. Watch the video to learn how to solve it! Source (in Spanish) …

By popular demand, I made a video for a problem getting a lot of news coverage! Sources …

This is a fun little geometry problem! DataGenetics http://datagenetics.com/blog/november22016/index.html How to solve the shape-shifting triangle …

It was #3 on Hilbert’s list of the most important problems in mathematics – until his student solved it. More links & stuff in full description below ↓↓↓ Featuring …

This is a nice probability question asked in an interview for a job at Amazon. Learn two ways to solve it! Source …

I saw this fun problem online. Watch the video for an “outside the box” solution! Source https://www.instagram.com/p/BxOfZBVB2Mo/ How To Solve The Square’s …

The problem is a little bit complex, but the answer is delightfully sur-pi-sing! Subscribe: https://www.youtube.com/user/MindYourDecisions?sub_confirmation=1 …

This was given to 13-14 year olds in Russia. Thanks to Egor Nazarov for suggesting this problem! Thanks to all patrons! Special thanks this month to Kyle, …

The Massachusetts Institute of Technology (MIT) is one of the top ranked universities in the world. A neat little algebra question appeared on its admissions …

James Grime has a card trick (and wants your help improving it). Get your first audiobook and 2 Audible Originals free when you try Audible for 30 days.

This is a fun problem I saw on Twitter. Watch to learn the solution! Sources https://twitter.com/le_becachel/status/1133463778790649857 …

There’s a short warm-up puzzle followed by the main puzzle. Thanks to Greg in Hungary (warm-up) and Jorn in Holland for suggesting these problems! *In my …

Featuring Professor Noga Alon. More links & stuff in full description below ↓↓↓ Extra footage: https://youtu.be/E-8YvnaumKU Recorded with Noga Alon at …

People are sharing a video about a US teacher who could not solve a problem from China’s university entrance exam, known as the gaokao. It’s a fairly …

I had many requests to solve problems like this. Watch the video to learn the trick! Sources …

People often email me that my videos helped them get a tech or finance job, which is really awesome, and I want to do more to help! So in this video I’m sharing …

Neil Sloane on the Van Eck Sequence… Check out Brilliant (get 20% off their premium service): https://brilliant.org/numberphile (sponsor) More links & stuff in full …

This problem stumped me! But it has a pretty nice solution. Thanks to all patrons! Special thanks this month to Kyle, Michael Anvari, Richard Ohnemus, Shrihari …

Edmund Harriss introduces a very cool tiling and talks about Tribonacci Numbers. More links & stuff in full description below ↓↓↓ Numberphile Podcast: …

This test question in England confused many 11 year old students, and even some teachers. Some of you may see the answer right away, but please be nice: it’s …

This equation is not true with decimal numbers. But what if we use other number bases? This viral math meme turns into a nice little puzzle, which, as they say, …

Ben Sparks discusses the math behind a curious problem…. Check out Brilliant (get 20% off their premium service): https://brilliant.org/numberphile (sponsor) …

I’ve posted about this type of problem before. But now I present a simple formula to solve for all values of r. Thanks to Tony Hasler for figuring out this method!

Congratulations to Daniel Mai for winning the 2019 Raytheon MATHCOUNTS National Competition! Here’s the question that sealed his victory. Source …

8th grade students in Turkey have to solve problems like this one. I admit I got the wrong answer! Can you figure it out? Thanks to Ata from Turkey who …