# Math

Since 2007, millions of people have watched videos on “how the Japanese multiply,” also known as “Chinese stick multiplication” or “Vedic Math.” With millions of people watching these videos, you would expect everything is known about this method. Surprisingly, there were neat tricks to be discovered! Last year I was the first person (to my

James Grime is back and talking prime numbers. Check out Brilliant.org by using the link: https://brilliant.org/numberphile (20% off premium subscription) More on prime numbers: http://bit.ly/primevids James Grime: http://singingbanana.com Editing by Pete McPartlan Music by Alan Stewart Read about Sierpinski Numbers: https://en.wikipedia.org/wiki/Sierpinski_number PrimeGrid: http://www.primegrid.com Numberphile is supported by the Mathematical Sciences Research Institute (MSRI): http://bit.ly/MSRINumberphile We

How many did you get correct? #shorts #math #maths #mathematics 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 purchase through these links, I may be compensated for purchases made on Amazon. As an Amazon Associate I earn from

How many triangles are too many? Featuring Henry Segerman from Oklahoma State University. More links & stuff in full description below ↓↓↓ Check Henry’s book about 3D printing math: http://amzn.to/2cWhY3R More Henry videos: http://bit.ly/Segerman_Videos Henry’s hinged doilies were joint work with Geoffrey Irving (https://naml.us) Support us on Patreon: http://www.patreon.com/numberphile NUMBERPHILE Website: http://www.numberphile.com/ Numberphile on Facebook:

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 original video, I solved for day 3 with AND but mistakenly wrote “OR”. Interestingly the OR is much easier to solve, and the answer works out to the same

Matt Parker has a new favourite number – again! More links & stuff in full description below ↓↓↓ Some notes from Matt on how far he has investigated: https://www.numberphile.com/cannon-ball-numbers Matt’s book “Humble Pi” via Maths Gear (signed and ships almost everywhere): http://bit.ly/Humble_Pi More Numberphile videos with Matt: http://bit.ly/Matt_Videos James Grime sphere packing: https://youtu.be/CROeIGfr3gs Lucas Numbers:

Mr. White, Mr. Blue, Mr. Brown and Mr. Pink are wearing shirts that match their names, but no one is wearing the same color shirt as their name. They exchange a few words that give hints about what color shirt each person is wearing. Can you figure it out? My blog post for this video:

Tadashi Tokieda is talking about Borromean links again – this time using ribbons. More links & stuff in full description below ↓↓↓ More Tadashi videos: http://bit.ly/tadashi_vids Knots: http://bit.ly/Knot-a-Phile Video by Brady Haran and Pete McPartlan (animations by Pete) Music by Alan Stewart Support us on Patreon: http://www.patreon.com/numberphile NUMBERPHILE Website: http://www.numberphile.com/ Numberphile on Facebook: http://www.facebook.com/numberphile Numberphile

Thanks to Alessio from Italy for creating this problem and sending it to me! A cyclist and a series of motorcycles are racing to the top of a long climb, and the cyclist doubles back. Given how many motorcycles passed the cyclist, can you figure out the motorcycles’ speed? (precise wording in video, too long

A quick little problem from Cliff Stoll, who baked a birthday cake for Brady… More links & stuff in full description below ↓↓↓ A trilogy of mathematical cake cutting videos… http://bit.ly/CakeCuttingTrilogy See more Cliff videos: http://bit.ly/Cliff_Videos The scientific way to cut a cake… https://youtu.be/wBU9N35ZHIw Numberphile is supported by the Mathematical Sciences Research Institute (MSRI): http://bit.ly/MSRINumberphile

Thank you for 100 million views! To celebrate, here’s a puzzle related to 100 million, sent by Karin. Find a sequence of 100 million consecutive non-prime numbers. That is, every number is composite—not a single number is a prime number. The method can actually be generalized for arbitrary lengths too! Watch the video for the

Do political beliefs affect mathematical ability!? More links & stuff in full description below ↓↓↓ Featuring Dr James Grime. Here is the paper referred to: http://bit.ly/wrecksmath Maths vs Math: http://bit.ly/MathorMaths Brown papers: http://bit.ly/brownpapers 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 Brady Haran Patreon: http://www.patreon.com/numberphile Brady’s videos subreddit: http://www.reddit.com/r/BradyHaran/

What’s the area bound by the lines x + y = 5, x + 2y = 6 and the y-axis? I present one way to solve this problem. #shorts 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 purchase

Here’s a fun game you can play with another person. The game starts on January 1. Each of two players takes turns calling out another date. The new date has to be a later date in the year with either the same month OR the same day (from January 1, a player can call out

Featuring Matt Parker… Part 2 (solution) here: https://youtu.be/pasyRUj7UwM More links & stuff in full description below ↓↓↓ Discuss this video on Brady’s subreddit: https://redd.it/6628q2 We appreciate any help on Patreon – it lets us make a few more and better videos: http://www.patreon.com/numberphile Matt Parker on Numberphile playlist: http://bit.ly/Matt_Videos Matt’s channel: http://bit.ly/StandUpMaths Parker Square T-Shirt: http://bit.ly/ParkerSquareTshirt

Every year some NBA team seems to make the playoffs with a losing or barely even record. This video considers how extreme the example can go. WATCH how an NFL team with 0 wins could make the playoffs: https://www.youtube.com/watch?v=3xXyauro_kc Worst nba playoff teams: http://www.sbnation.com/nba/2014/4/4/5581984/nba-playoffs-history-bulls-spurs-knicks-cavaliers NBA scheduling: http://www.nbastuffer.com/component/option,com_glossary/Itemid,0/catid,44/func,view/term,How%20the%20NBA%20Schedule%20is%20Made/ If you like my videos, you can support

This is a tricky SAT/GRE type problem that most people miss. Can you figure it out? Desmos animation https://www.desmos.com/calculator/kiswg6p0q7 Sources https://www.thisisinsider.com/hard-sat-math-questions-test-practice-2018-3 https://www.prepscholar.com/gre/blog/gre-geometry-review-practice/ Subscribe: https://www.youtube.com/user/MindYourDecisions?sub_confirmation=1 Playlist to watch all videos on MindYourDecisions: https://www.youtube.com/playlist?list=UUHnj59g7jezwTy5GeL8EA_g This is the only channel to feature math topics suggested by people around the world. Support on Patreon to inspire mathematical discovery and

Featuring Neil Sloane from the OEIS. Check out Brilliant (get 20% off their premium service): https://brilliant.org/numberphile (sponsor)… More links & stuff in full description below ↓↓↓ Part 2: https://youtu.be/HFeKdMf01rQ Neil Sloane is the founder of the The On-Line Encyclopedia of Integer Sequences. Visit it here: https://oeis.org More Neil Sloane on Numberphile: http://bit.ly/Sloane_Numberphile Numberphile is supported

Lattice multiplication is a fast and easy way to multiply numbers and even polynomials. You write the digits of one number as different columns and the digits of the other number as different rows. Then you multiply the digits in the columns and the rows, one by one, and add up the numbers diagonally. The

Part One: https://youtu.be/wGkvyN6s9cY Featuring Tadashi Tokieda. More links & stuff in full description below ↓↓↓ More Tadashi videos: http://bit.ly/tadashi_vids Raw paperclips slow motions: https://youtu.be/zuX5yy_93JA 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

First watch how to calculate cube roots: https://www.youtube.com/watch?v=Ds8ijPsg26g 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 Blog: http://mindyourdecisions.com/blog/ Twitter: http://twitter.com/preshtalwalkar

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 to Zaki for suggesting this problem. 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! Why are some

Some of your favourite maths jokes are dissected in forensic fashion. More links & stuff in full description below ↓↓↓ It is YouTube Comedy Week: http://yt.be/comedyweek Animation by Pete McPartlan – http://www.petemcpartlan.co.uk Explanations by Matt Parker – http://www.standupmaths.com More jokes explained at: http://youtu.be/Fmb3TCvlET Leave more joke suggestions in the comment section. NUMBERPHILE Website: http://www.numberphile.com/ Numberphile

A geometry textbook has the following problem: “A right triangle has a hypotenuse equal to 10 and an altitude to the hypotenuse equal to 6. What is the area of the triangle?” Can you figure out the correct answer? Blog post (text/image explanation): http://wp.me/p6aMk-4t8 Special thanks to the following patrons! Kyle Alberto Nishikawa Brian M.

Here are more pics of the doodle: http://bit.ly/Doodle_Images More links & stuff in full description below ↓↓↓ And make sure you subscribe to Objectivity: https://www.youtube.com/c/objectivityvideos Thanks to Keith Moore at the Royal Society – https://royalsociety.org 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

Thanks to James for the suggestion! If a hen and a half lay an egg and a half in a day and a half how many eggs would one hen lay in one day? #math #maths #mathematics #shorts Sources https://www.mathsisfun.com/puzzles/one-and-a-half-hens-solution.html https://en.wikipedia.org/wiki/Conversion_of_units Subscribe: https://www.youtube.com/user/MindYourDecisions?sub_confirmation=1 Send me suggestions by email (address at end of many videos). I

The legendary Don Knuth on the Dragon Curve and learning from his mistakes. More links & stuff in full description below ↓↓↓ Reddit discussion: http://redd.it/2qt0f4 More Dragon Curve: http://bit.ly/DragonList Don Knuth’s book “Selected Papers on Fun and Games” has an excellent chapter going into this in more detail. Buy in US: http://amzn.to/149fBnL Buy in UK:

Thanks to Mohnish for the suggestion! This is a delightful geometry problem. Special thanks this month to: Mike Robertson, Daniel Lewis, Robert Zarnke, Kyle, Lee Redden. Thanks to all supporters on Patreon! http://www.patreon.com/mindyourdecisions 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

Make the equation correct by adding one blue dot, or erasing one blue dot. A single dot changes everything! Keep It 💯 Puzzle: 4 dots to make this true! Sources One of these pixels on the scoreboard should be either turned off or turned on. from mathpuzzles https://www.ocf.berkeley.edu/~wwu/cgi-bin/yabb/YaBB.cgi?board=riddles_medium;action=display;num=1091299465 https://www.utest.com/forums/11636/page/1 Playlist to watch all videos on

Thanks Squarespace: https://www.squarespace.com/numberphile More links & stuff in full description below ↓↓↓ Full length colouring video: https://youtu.be/a-6oOVdU7Oo Alex Bellos books (including colouring books): http://bit.ly/BellosBooks Colouring by Tiffany Arment: https://twitter.com/tiffanyarment (or coloring as it is America!) Thanks to Loretta Kolakoski for pictures of William (Bill). OEIS entry: https://oeis.org/A000002 Oldenburger paper (1939) pre-dating Kolakoski: http://www.ams.org/journals/tran/1939-046-00/S0002-9947-1939-0000352-9/S0002-9947-1939-0000352-9.pdf (the sequence

Which point minimizes the sum to 4 given points on a rectangle? Thanks to Chanul for suggesting this problem, which is adapted from a Sri Lankan Olympiad question. Special thanks this month to: Michael Anvari, Kyle. Thanks to all supporters on Patreon! http://www.patreon.com/mindyourdecisions References Geometric median https://en.wikipedia.org/wiki/Geometric_median Plastria, Frank. (2006). Four-point Fermat location problems revisited.

Probability expert Professor Persi Diaconis (Stanford University) talking about dice. More links & stuff in full description below ↓↓↓ Part 2: https://youtu.be/8UUPlImm0dM Tadashi and Dice: https://youtu.be/zzKGnuvX6IQ More dice videos: http://bit.ly/Dice_Videos More Persi Diaconi videos: http://bit.ly/Persi_Videos Diaconis/Keller paper on fair dice: http://bit.ly/FairDicePaper 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:

This question appeared on the October 1980 SAT exam. Like all questions, it was supposed to have exactly one correct answer. However the test-makers made a mistake. Can you figure out what they did wrong? Blog post (text explanation): http://wp.me/p6aMk-4vX Source Fiske, Edward B. “A Second Student Wins Challenge on Answer To Math Exam Problem.”

Dr James Grime and a handy trick for checking calculations. Ditch the nines… More links & stuff in full description below ↓↓↓ Some extra footage from this interview: https://youtu.be/wQsQ8joretY 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

The game starts with 6 empty glasses in a row numbered 1 to 6. You roll a standard die. If the number for the glass is empty, then the glass is filled up. If the number for the glass is full, then you drink that glass. There is a special rule when 5 glasses are

Get your first audiobook free with an Audible 30-day trial. Go to http://www.audible.com/numberphile or text numberphile to 500 500. More links & stuff in full description below ↓↓↓ This video features Edmund Harriss from University of Arkansas. Extra footage from this interview: https://youtu.be/7ehaadVtaMI Heesch’s Tiling Problem by Casey Mann: http://faculty.washington.edu/cemann/Heesch.pdf Check out the Numberphile Podcast:

This is a tricky but fun geometry problem! Special thanks this month to: Michael Anvari, Kyle. Thanks to all supporters on Patreon! http://www.patreon.com/mindyourdecisions Adapted from Math Kangaroo paper problem 22 https://www.mathkangaroo.in/media/pdf/16556_Grade_8_Math_Kangaroo_Sample_Paper_-2019.pdf STEM4all video 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

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 Blog: http://mindyourdecisions.com/blog/ Twitter: http://twitter.com/preshtalwalkar Facebook: https://www.facebook.com/pages/Mind-Your-Decisions/168446714965 Google+: https://plus.google.com/108336608566588374147/posts Pinterest: https://www.pinterest.com/preshtalwalkar/ Tumblr: http://preshtalwalkar.tumblr.com/

James Grime on the Hadwiger–Nelson problem. Check out Brilliant (get 20% off their premium service): https://brilliant.org/numberphile (sponsor) Extra footage from this interview: https://youtu.be/7nBtRKvUox4 The Four Color Map Theorem: https://youtu.be/NgbK43jB4rQ More on James Grime (you can book him for talks): http://singingbanana.com More James Grime videos: http://bit.ly/grimevideos The de Grey paper: https://arxiv.org/abs/1804.02385 A good write up on

This problem seems like it is impossible to solve because it does not have enough information. If the rectangle has an area of 10, what is the area of the triangle? After posting the video, I was told 2001 AMC 12 problem 22 was nearly the same problem: https://artofproblemsolving.com/wiki/index.php/2001_AMC_12_Problems/Problem_22 Subscribe: https://www.youtube.com/user/MindYourDecisions?sub_confirmation=1 Send me suggestions by

Continuing on from Zvezda’s previous video about Ptolemey’s Theorem (see: https://youtu.be/bJOuzqu3MUQ) now we use it to prove some cool stuff with pentagons and equilateral triangles. More links & stuff in full description below ↓↓↓ Zvezda’s Numberphile playlist: http://bit.ly/zvezda_videos Zvezda’s webpage: https://math.berkeley.edu/~stankova/ Golden Ratio: https://youtu.be/sj8Sg8qnjOg Epic Circles: https://youtu.be/sG_6nlMZ8f4 Triangle Magic Highway: https://youtu.be/wVH4MS6v23U Numberphile is supported by

The Braess Paradox is an unexpected result from network theory. It states that adding capacity could actually slow down the speed of the network. Applied to highways, the Braess Paradox means the existence of some roads slows down traffic, or that closing some roads could speed up traffic. The Braess Paradox can also explain the

Johnny Ball is back talking about Hippocrates, Lunes, and a Fancy Q. More links & stuff in full description below ↓↓↓ Johnny Ball’s website: https://johnnyball.co.uk More Johnny on Numberphile: https://bit.ly/Johnny_Ball An earlier Lunes video we did with Barry Mazur: https://www.youtube.com/watch?v=n_FsAwvxBI8 Numberphile is supported by the Mathematical Sciences Research Institute (MSRI): http://bit.ly/MSRINumberphile We are also supported

Thanks to Pedro in Argentina for suggesting this! The problem is adapted from the TESBA test. It’s a fun one! Sources https://en.wikipedia.org/wiki/Argentina#/media/File:Flag_of_Argentina.svg https://en.wikipedia.org/wiki/Argentina#/media/File:Argentina_orthographic.svg http://www-news.uchicago.edu/releases/98/980417.calderon.shtml 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! Why are some comments before the video is published? Get early access and

Can you solve this tricky question? #maths #math #mathematics #shorts Hardest GCSE maths questions list (Edexcel June 2018 Higher Paper 1 – Question 6) Top 5 Hardest GCSE Maths Questions in 2022 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!

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