Math

Alex’s book: http://amzn.to/1l0yX46 The Curta is a pocket-sized, mechanical, digital calculator!!! It was invented by Curt Herzstark. More links & stuff in full description below ↓↓↓ Shown here by Alex Bellos, author of Alex’s Adventures in Numberland. More about our contributors, including Alex, at http://www.numberphile.com/team/index.html NUMBERPHILE Website: http://www.numberphile.com/ Numberphile on Facebook: http://www.facebook.com/numberphile Numberphile tweets: https://twitter.com/numberphile

Thanks to Lucas for suggesting this problem! It comes from a Belgian Olympiad problem for 16 to 18 year old students. Subscribe: https://www.youtube.com/user/MindYourDecisions?sub_confirmation=1 Send me suggestions by email (address in video). I consider all ideas though can’t always reply! Like many YouTubers I use popular software to prepare my videos. You can search for animation

Featuring Professor Hannah Fry – more details on her work below. Check out Brilliant (get 20% off their premium service): https://brilliant.org/numberphile (sponsor) More links & stuff in full description below ↓↓↓ Hannah Fry: https://hannahfry.co.uk Hannah’s books: https://amzn.to/3ArNEaA Her latest is Rutherford and Fry’s Complete Guide to Absolutely Everything: https://amzn.to/3tSvYDN More Hannah Fry on Numberphile: http://bit.ly/hannah_vids

Squarespace: http://www.squarespace.com/numberphile This video features Hannah Fry – https://twitter.com/fryrsquared More links & stuff in full description below ↓↓↓ More on this topic (and lizards): http://youtu.be/Z8lv2vy5vco And even more on this topic: http://youtu.be/ygHwBxWyI6E The paper: http://bit.ly/RPSpaper Reddit for this video: http://redd.it/2tq25k Art and animation by Pete McPartlan Support us on Patreon: http://www.patreon.com/numberphile NUMBERPHILE Website: http://www.numberphile.com/ Numberphile

These are the answers to the previous video with 3 matchstick puzzlers. If you like my videos, you can support me at Patreon: http://www.patreon.com/mindyourdecisions Connect on social media. I update each site when I have a new video or blog post, so you can follow me on whichever method is most convenient for you. My

Another pass at the Monty Hall Problem – see the last video and a new “express explanation” at: http://bit.ly/MontyHallProb More links & stuff in full description below ↓↓↓ Support us on Patreon: http://www.patreon.com/numberphile NUMBERPHILE Website: http://www.numberphile.com/ Numberphile on Facebook: http://www.facebook.com/numberphile Numberphile tweets: https://twitter.com/numberphile Subscribe: http://bit.ly/Numberphile_Sub Numberphile is supported by the Mathematical Sciences Research Institute (MSRI):

What is the radius of each sphere? Reference http://puzzling.stackexchange.com/questions/41952/nine-identical-spheres-fit-exactly-into-a-cube Subscribe: https://www.youtube.com/user/MindYourDecisions?sub_confirmation=1 Send me suggestions by email (address in video). I consider all ideas though can’t always reply! Like many YouTubers I use popular software to prepare my videos. You can search for animation software tutorials on YouTube to learn how to make videos. Be prepared–animation

Thanks to Umesh for the suggestion! If the large circle has a radius equal to 1, what is the radius of each small circle? Subscribe: https://www.youtube.com/user/MindYourDecisions?sub_confirmation=1 Send me suggestions by email (address at end of many videos). I may not reply but I do consider all ideas! If you buy from the links below I

Can you solve this “coffin” problem? Thanks to Rahul for the suggestion! Special thanks this month to: Kyle, Mike Robertson, Michael Anvari. Thanks to all supporters on Patreon! http://www.patreon.com/mindyourdecisions Adapted from problem 4 of Jewish Problems by Tanya Khovanova, Alexey Radul https://arxiv.org/abs/1110.1556v2 Coffin Problem ft. blackpenredpen: Cube and Cube Root (Mu Prime Math) Subscribe: https://www.youtube.com/user/MindYourDecisions?sub_confirmation=1

Happy Pi Day! At 3/14/15 at 9:26 the time will be accurate to pi for 7 decimal places. What’s your favorite fact about pi? Links to proofs and more below in the description. 1. The definition 00:10 Related: the area of circle intuitive explanation 2. Pi is irrational 00:47 Proof (video) Proof (blog post) Proving

I bet this one will give many adults a good challenge too. Thanks to Pett for the suggestion! Special thanks this month to: Kyle, Mike Robertson, Michael Anvari, Daniel Lewis, Robert Zarnke. Thanks to all supporters on Patreon! http://www.patreon.com/mindyourdecisions Singapore International Math Olympiad Challenge (SIMOC) 2015 – Primary 5 Paper, problem 24. Sample Papers Subscribe:

A ‘math metal’ song about the golden ratio (aka Phi). More links & stuff in full description below ↓↓↓ See more about the making of the song and maths behind it at: http://www.youtube.com/watch?v=mqK63v2Jzks This was a collaboration with the excellent Dave Brown – his channel is: http://www.youtube.com/user/wwwboyinabandcom (check it out!!!) Also featuring Professor Phil Moriarty

We’re exploring the world of Chicken Nuggets and Frobenius numbers. 43 has long been a special number in the world of McNugget mathematics, but 11 is also important! More links & stuff in full description below ↓↓↓ This video features Dr James Grime. NUMBERPHILE Website: http://www.numberphile.com/ Numberphile on Facebook: http://www.facebook.com/numberphile Numberphile tweets: https://twitter.com/numberphile Subscribe: http://bit.ly/Numberphile_Sub

Featuring Grant Sanderson, creator of 3blue1brown. Extra footage from this interview: https://youtu.be/pJyKM-7IgAU 3blue1brown video on the shadow a cube: https://youtu.be/ltLUadnCyi0 More links & stuff in full description below ↓↓↓ 3blue1brown: https://www.youtube.com/channel/UCYO_jab_esuFRV4b17AJtAw Grant on The Numberphile Podcast: https://youtu.be/A0RH93XvSyU Numberphile is supported by the Mathematical Sciences Research Institute (MSRI): http://bit.ly/MSRINumberphile We are also supported by Science Sandbox,

What value is each letter? This is an incredible math problem with just a single solution! Can you figure it out? My blog post for this video https://wp.me/p6aMk-85e Websites consulted http://mathforum.org/library/drmath/view/60417.html https://en.wikipedia.org/wiki/Verbal_arithmetic#Solving_cryptarithms Playlist to watch all videos on MindYourDecisions This is the only channel to feature math topics suggested by people around the world. Support

Featuring Neil Sloane. Visit https://gift.climeworks.com/numberphile to give the gift of CO₂ removal. Use code NUMBERPHILE10 for 10% off your purchase in December (sponsor) More links & stuff in full description below ↓↓↓ Neil Sloane is the founder of The OEIS: https://oeis.org More videos with Neil: http://bit.ly/Sloane_Numberphile Prime Playlist: https://bit.ly/PrimePlaylist Note the 17350-digit prime we feature

Thanks to Peter for sending me this problem! This is a really fun one and I encourage you to work it out. A priest and a cantor have a conversation about the product and sum of three visitors. After a few exchanges, the cantor figures out the visitors ages. But wait, how old is the

More links & stuff in full description below ↓↓↓ Brady’s Movember Page: http://bit.ly/BradyMo See full description for list of Connect 4 links. John Tromp’s page: http://bit.ly/TrompNumberphile James Allen’s Connect Four book: http://bit.ly/AllenBook James Allen: http://james.fabpedigree.com/ OEIS: https://oeis.org/A212693 Victor Allis paper: http://bit.ly/AllisPaper NUMBERPHILE Website: http://www.numberphile.com/ Numberphile on Facebook: http://www.facebook.com/numberphile Numberphile tweets: https://twitter.com/numberphile Subscribe: http://bit.ly/Numberphile_Sub Videos by

Thanks to John H. for the suggestion! A square is inscribed in a quarter circle with two of its vertices on the arc. If the radius equals 1, what is the area of the square? Special thanks this month to: Robert Zarnke, Kyle, Mike Robertson, Michael Anvari, Daniel Lewis. Thanks to all supporters on Patreon!

The tin asks: “What’s the biggest number you can make?” Sounds like a challenge! More links & stuff in full description below ↓↓↓ Ebay link: AUCTION OVER Fate of the spaghetti (not pleasant): http://youtu.be/tsbHenS5CUs Brady reads the whole number: http://youtu.be/uN2U9PQUGB0 The people at Heinz had nothing to do with his video – I just saw

Recently Russia’s Prime Minister Mikhail Mishustin visited 11th grade students (about 17-18 years old) and asked them a challenging geometry problem. Can you figure it out? I came across this puzzle in Alex Bellos’s column on The Guardian. He has a new book that I wanted to share titled “The Language Lover’s Puzzle Book.” I

Johnny Ball on the “often missed” Hippocrates of Chios. Check out Brilliant (get 20% off their premium service): https://brilliant.org/numberphile (sponsor) More links & stuff in full description below ↓↓↓ More on Johnny Ball, including his books and live shows: https://www.johnnyball.co.uk See Johnny discuss Russian multiplication: https://youtu.be/HJ_PP5rqLg0 Numberphile is supported by the Mathematical Sciences Research Institute

Photomath can’t solve this, and neither can Mathway, Symbolab, or Desmos. Can you? I explain how you can. A similar problem was given to high school students in Massachusetts, and you really have to know what you’re doing to figure it out. Thanks to all patrons! Special thanks this month to: Shrihari Puranik Richard Ohnemus

If a semicircle and its flipped copy are placed side by side, how much distance do they span from end to end? This is a neat problem adapted from a Mathematical Olympiad Qualifying Test in the Philippines. Can you figure it out? Subscribe: https://www.youtube.com/user/MindYourDecisions?sub_confirmation=1 Send me suggestions by email (address at end of many videos).

Featuring Hannah Fry discusses Train Graphs. More links & stuff in full description below ↓↓↓ Hannah’s website, including links to her many and varied projects… and latest books: https://hannahfry.co.uk Her latest book (with Adam Rutherford) is the Complete Guide to Absolutely Everything (Abridged): https://amzn.to/30Mr6UE Hannah on Numberphile: http://bit.ly/hannah_vids Hannah on the Numberphile podcast: https://youtu.be/KKCjQWmUwv8 Numberphile

Matt Parker talks about numbers – as he often does. His book “Humble Pi” is at: http://bit.ly/Humble_Pi More links & stuff in full description below ↓↓↓ The book on Amazon: https://amzn.to/2NKposg Numberphile podcast is on your podcast player. Or the website is: https://www.numberphile.com/podcast And it’s on YouTube too: http://bit.ly/Numberphile_Pod_Playlist The Knight’s Tour T-Shirt is in

Thanks to Jumar for the suggestion! Can you solve this interesting geometry problem? 0:00 Problem 1:10 Similar triangles 2:29 Solution Subscribe: https://www.youtube.com/user/MindYourDecisions?sub_confirmation=1 Send me suggestions by email (address at end of many videos). I may not reply but I do consider all ideas! If you buy from the links below I may receive a commission

Thanks to George Tan for suggesting this problem! It is from the 2019 SPM paper in Malaysia. Many students cried after taking the exam, and many teachers found the problems to be very challenging as well. (This means the problems were hard given the syllabus and expectations of the exam–no need to let us know

This is a nice little logic puzzle from Terry Stickels! Books by Terry Stickels (including “Contemporary Brainteasers”) http://www.terrystickels.com/books.html Subscribe: https://www.youtube.com/user/MindYourDecisions?sub_confirmation=1 Send me suggestions by email (address in video). I consider all ideas though can’t always reply! Like many YouTubers I use popular software to prepare my videos. You can search for animation software tutorials on

Professor Tony Padilla is back with another epic number. Our Big Number playlist of previous videos: http://bit.ly/Big_Numbers More links & stuff in full description below ↓↓↓ Busy Beavers on Computerphile: https://youtu.be/CE8UhcyJS0I With thanks to Agustín Rayo himself. Read more from Prof Rayo at: http://web.mit.edu/arayo/www/bignums.html And see his website at: https://arayo.scripts.mit.edu/home/ Tony Padilla: https://twitter.com/DrTonyPadilla Numberphile is

Thanks to Francisco from Portugal for the suggestion! They say Euler asked this tricky algebra problem to his students. Reference https://blogs.helsinki.fi/kulikov/2010/06/16/eulers-riddle/ Subscribe: https://www.youtube.com/user/MindYourDecisions?sub_confirmation=1 Send me suggestions by email (address in video). I consider all ideas though can’t always reply! Like many YouTubers I use popular software to prepare my videos. You can search for animation

An evil warden holds you prisoner, but offers you a chance to escape. There are 3 doors A, B, and C. Two of the doors lead to freedom and the third door leads to lifetime imprisonment, but you do not which door is what type. You are allowed to point to a door and ask

Tadashi is back, this time looking at drooping paper (and toilet paper). More links & stuff in full description below ↓↓↓ Subscribe to Numberphile and never miss a floppy paper video: http://bit.ly/Numberphile_Sub Playlist of Tadashi Tokieda videos: http://bit.ly/tadashi_vids Pizza and Gaussian curvature: https://youtu.be/gi-TBlh44gY Support us on Patreon: http://www.patreon.com/numberphile NUMBERPHILE Website: http://www.numberphile.com/ Numberphile on Facebook: http://www.facebook.com/numberphile

Check our sponsor The Great Courses Plus (free trial): http://ow.ly/j5cB30hIvm2 This video features Cliff Stoll. More links & stuff in full description below ↓↓↓ More Cliff Stoll videos: http://bit.ly/Cliff_Videos Buy a Klein Bottle from Cliff – it’s an experience: http://www.kleinbottle.com Discuss this video on Brady’s subreddit: https://redd.it/96x6c4 Numberphile is supported by the Mathematical Sciences Research

Hippocrates of Chios solved this, nearly 100 years before Euclid even wrote The Elements, and before we knew the exact formula for the area of a circle. This is said to be the first precise mathematical of the area between two curved lines. Learn how he solved for the area of a crescent-shaped lune (same

Thanks to Nikhil Patro for suggesting this problem! What is the sum of the corner angles in a regular 5-sided star? What if the star is not regular, what is the sum of corner angles then? There are some neat ways to solve this. I present my favorite methods. Thanks to all patrons! Special thanks

The abc Conjecture may have been proven by a Japanese mathematician – but what is it? More links & stuff in full description below ↓↓↓ Feeling brave and want to read the papers by Shinichi Mochizuki – http://www.kurims.kyoto-u.ac.jp/~motizuki/papers-english.html (scroll to the bottom) This video features Dr James Grime who tweets at https://twitter.com/jamesgrime NUMBERPHILE Website: http://www.numberphile.com/

Albert Einstein was challenged with a simple riddle in a 1934 correspondence with the psychologist Max Wertheimer. Can you figure it out? Thanks to all patrons! Special thanks to: Shrihari Puranik, Richard Ohnemus, Michael Anvari, Kyle. We are the only channel to feature math topics suggested by people around the world. Support on Patreon to

In the past 5 months, all of Mark Rober’s videos have been #1 trending on YouTube. He put his success in perspective by analogy to a statistical experiment of flipping coins. Some people pointed out the calculation wasn’t quite correct, so I thought it would be a great topic for a video. Mark Rober tweet

Fields Medallist and math “celebrity” Cédric Villani is famous for wearing ornate spiders on his lapel. More Villani videos: http://bit.ly/Villani_Videos Cédric Villani website: http://cedricvillani.org His book Birth of a Theorem (Amazon): http://bit.ly/BirthOfATheorem Villani talks about his Fields Medal: https://youtu.be/Vp3sgYKULp0 Numberphile is supported by the Mathematical Sciences Research Institute (MSRI): http://bit.ly/MSRINumberphile We are also supported by

Featuring Professor Howard Masur from the University of Chicago. Filmed at the Mathematical Sciences Research Institute (MSRI). Part 2 of this interview: https://youtu.be/AGX0cLbHaog Patreon: http://www.patreon.com/numberphile Numberphile is supported by the Mathematical Sciences Research Institute (MSRI): http://bit.ly/MSRINumberphile We are also supported by Science Sandbox, a Simons Foundation initiative dedicated to engaging everyone with the process of

The famed Poincaré Conjecture – the only Millennium Problem cracked thus far. More links & stuff in full description below ↓↓↓ Ricci Flow (used to solve the problem): http://youtu.be/hwOCqA9Xw6A Riemann Hypothesis: http://youtu.be/d6c6uIyieoo Extra interview footage with Jim Isenberg: http://youtu.be/7eJleW0JcKg Grigori Perelman’s paper: http://bit.ly/perelmanpaper Discussed here by Katie Steckles and James Isenberg. Support us on Patreon:

How do you measure the length of a spiral on a cylinder? There is a neat trick! If you like my videos, you can support me at Patreon: http://www.patreon.com/mindyourdecisions Connect on social media. I update each site when I have a new video or blog post, so you can follow me on whichever method is

This problem is adapted from an Oxford University admissions question. They say if you can solve this in your head, you are a genius 😉 Alex Bellos’s column on The Guardian https://www.theguardian.com/science/2021/jul/12/did-you-solve-it-oxford-university-admissions-questions Subscribe: https://www.youtube.com/user/MindYourDecisions?sub_confirmation=1 Send me suggestions by email (address at end of many videos). I may not reply but I do consider all ideas!

Tadashi Tokieda puts $20 on the line… More links & stuff in full description below ↓↓↓ More Tadashi videos: http://bit.ly/tadashi_vids Paperclips: https://youtu.be/wGkvyN6s9cY Video by Brady Haran and Pete McPartlan (animations by Pete) Support us on Patreon: http://www.patreon.com/numberphile NUMBERPHILE Website: http://www.numberphile.com/ Numberphile on Facebook: http://www.facebook.com/numberphile Numberphile tweets: https://twitter.com/numberphile Subscribe: http://bit.ly/Numberphile_Sub Numberphile is supported by the Mathematical