The area when two circles square off

Can you solve for the area of the square and the length of the tangent line? Special thanks this month to Fiona Harper, Kyle, Mike Robertson, Michael Anvari, Robert Zarnke. Thanks to all supporters on Patreon! http://www.patreon.com/mindyourdecisions Adapted from a puzzle by Twitter @Cshearer41 (Catriona Agg) A semicircle and quarter circle inside a square. How […]

Planing Sequences (Le Rabot) – Numberphile

Featuring Neil Sloane from the OEIS – and his carpenter’s plane. Mandelbrot papers offer: https://www.patreon.com/posts/52011294 More links & stuff in full description below ↓↓↓ More Neil Sloane videos: http://bit.ly/Sloane_Numberphile The OEIS: https://oeis.org Discuss this video on Brady’s subreddit: https://redd.it/nrba65 Numberphile is supported by the Mathematical Sciences Research Institute (MSRI): http://bit.ly/MSRINumberphile We are also supported by […]

Parabolas and Archimedes – Numberphile

This video features Johnny Ball. Check out Brilliant (get 20% off their premium service): https://brilliant.org/numberphile (sponsor) More links & stuff in full description below ↓↓↓ Johnny Ball: https://johnnyball.co.uk More Numberphile videos with Johnny Ball: http://bit.ly/Johnny_Ball Johnny Ball books: https://amzn.to/3v8Xxqx Numberphile is supported by the Mathematical Sciences Research Institute (MSRI): http://bit.ly/MSRINumberphile We are also supported by […]

A Tricky Puzzle Solved In 2 Ways!

I received many requests for this challenging problem. Can you solve it? Thanks to Toli for the suggestion! Geometry solution in method 1 http://128.192.17.191/EMT668/EMAT6680.F99/Estes/15degrees/15degreesgeometric.html Another geometry solution http://128.192.17.191/EMT668/EMAT6680.F99/Estes/15degrees/solution2.html Trigonometry solution http://128.192.17.191/EMT668/EMAT6680.F99/Estes/15degrees/15degreestrigonometric.html Go Geometry discussion https://gogeometry.blogspot.com/2009/11/problem-395-square-15-degree.html https://drive.google.com/file/d/1A0Az5nJ9wGBwcM2F4gQY2dSfeKJZ1gSS/view 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 […]

Gambling with the Martingale Strategy – Numberphile

Tom Crawford discussing roulette and gambling with a famed strategy. More Tom videos on Numberphile: http://bit.ly/Crawford_Videos More links & stuff in full description below ↓↓↓ Tom Crawford’s website, with links to his work and other outreach: https://tomrocksmaths.com Numberphile is supported by the Mathematical Sciences Research Institute (MSRI): http://bit.ly/MSRINumberphile We are also supported by Science Sandbox, […]

A fun sum of sums

Can you solve this tricky algebra problem? 0:00 Problem 0:49 Hints 4:12 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 for sales. (As an Amazon Associate I […]

A Sequence with a Mistake – Numberphile

Sequence guru Neil Sloane on a sequence which puzzled him – until he spotted the mistake! More links & stuff in full description below ↓↓↓ More Neil Sloane videos: http://bit.ly/Sloane_Numberphile The OEIS: https://oeis.org Hanny’s Voorwerp: https://youtu.be/RDr6bSB6Vlg Numberphile is supported by the Mathematical Sciences Research Institute (MSRI): http://bit.ly/MSRINumberphile We are also supported by Science Sandbox, a […]

A Mesmerizing Area Puzzle

This problem is adapted from the first round of the 2017 Dutch Maths Olympiad. Special thanks this month to: Robert Zarnke, Marq Short, Kyle, Mike Robertson, Michael Anvari. Thanks to all supporters on Patreon! http://www.patreon.com/mindyourdecisions Reddit Math Riddles Simple square puzzle from mathriddles Subscribe: https://www.youtube.com/user/MindYourDecisions?sub_confirmation=1 Send me suggestions by email (address at end of many […]

The “Impossible” Ages of Sisters Puzzle

Asha and Lata are two sisters with mathematically interesting ages. If you write Lata’s age after Asha’s, you get a 4 digit perfect square. Amazingly the same thing happens if you repeat the exercise in 11 years. How old are Asha and Lata currently? 0:00 Problem 1:09 Difference of squares 2:25 Solution Subscribe: https://www.youtube.com/user/MindYourDecisions?sub_confirmation=1 Send […]

The Math of Being a Pig – Numberphile

Featuring Ben Sparks. Check out https://www.kiwico.com/Numberphile and get 50% off your first month of any subscription. More links & stuff in full description below ↓↓↓ Extra footage from the making of this video (including Brady trying to roll 50 points and his game against the online Pig Player): https://youtu.be/zD9-V9Idbug Ben Sparks: https://www.bensparks.co.uk More Ben Sparks […]

The challenging 7 squares puzzle from Vietnam

Thanks to Thinh for suggesting this problem! What is the area of a single square? A version of this was given to 12-13 year olds in Vietnam. I admit I didn’t see the trick, but it is a fun one! VN Express (in Vietnamese) https://vnexpress.net/bai-toan-cau-kinh-7-o-vuong-4169822.html Subscribe: https://www.youtube.com/user/MindYourDecisions?sub_confirmation=1 Send me suggestions by email (address at end […]

A tricky problem with a “divine” answer!

Can you solve this equation? Thanks to Hrigved for the suggestion! Reference https://math.stackexchange.com/questions/438452/find-all-real-numbers-such-that-sqrtx-frac1x-sqrt1-frac1x 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 for sales. (As an Amazon Associate I […]

Eureka Sequences – Numberphile

OEIS founder Neil Sloane with more sequences to ponder – of course! Check out Brilliant (get 20% off their premium service): https://brilliant.org/numberphile (sponsor) More links & stuff in full description below ↓↓↓ More Neil Sloane videos: http://bit.ly/Sloane_Numberphile Visit the OEIS: https://oeis.org/ Today’s featured sequences: https://oeis.org/A008864 and https://oeis.org/A001043 Numberphile is supported by the Mathematical Sciences Research […]

The Levine Sequence – Numberphile

Neil Sloane from the OEIS has another number sequence which escalates quickly. More links & stuff in full description below ↓↓↓ More videos with Neil Sloane: http://bit.ly/Sloane_Numberphile Levine’s sequence on the OEIS: https://oeis.org/A011784 Neil is the founder and keeper of the The On-Line Encyclopedia of Integer Sequences: https://oeis.org/ Numberphile Podcast: https://www.numberphile.com/podcast Unmade Podcast: https://www.unmade.fm/ Numberphile […]

Only 6% Solved This

This is a fun algebra problem. Can you figure it out? Thanks to Aslah from India for the suggestion! 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 for […]

Zig-Zag Line Puzzle

Can you solve this geometry problem? Thanks to Lucas from Brazil for the suggestion! Kangaroo Maths 2020 https://www.matematica.pt/en/docs/kangaroo/enunciados/2020/2020_Grade9-10.pdf Proof of inscribed angle theorem https://www.khanacademy.org/math/geometry/hs-geo-circles/hs-geo-inscribed-angles/a/inscribed-and-central-angles-proof 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 […]

Nightingale Diagrams – Numberphile

Professor Mike Merrifield discusses diagrams popularized by Florence Nightingale. Check out Brilliant (get 20% off their premium service): https://brilliant.org/numberphile (sponsor) More links & stuff in full description below ↓↓↓ Professor Mike Merrifield is an astronomer at the University of Nottingham, UK. He’s updating his own Nightingale diagram regularly on Twitter: https://twitter.com/AstroMikeMerri More videos with Mike: […]

Cuneiform Numbers – Numberphile

Alex Bellos discusses how numbers were written in ancient Cuneiform. More links & stuff in full description below ↓↓↓ More from this interview on Numberphile2: https://youtu.be/n-sxOVSZc-Q Alex Bellos website: http://www.alexbellos.com And his books on Amazon (including the Language Lovers Puzzle Book which features cuneiform): https://amzn.to/3czJjXl More Alex Bellos on Numberphile: http://bit.ly/Bellos_Playlist Search the British Museum […]

Legendary test question – π is less than 22/7

Happy #PiDay! When two of the hardest tests in the world cover the same problem, you know it’s a big deal. References Wikipedia article https://en.wikipedia.org/wiki/Proof_that_22/7_exceeds_%CF%80 Putnam exam 1968 A1 https://prase.cz/kalva/putnam/putn68.html JEE Advanced 2010 Paper Solutions Part-1 | IIT-JEE | Strategy, Tips, & Tricks | Paper Discussion (see around 55:30) Proving 22/7 is greater than PI […]

All the World’s Coronavirus fits in a Coke Can – Numberphile

Kit Yates explains how he calculated that all the SARS-CoV-2 in the world would fit inside a Coke can – and discusses “Fermi Estimates”. More links & stuff in full description below ↓↓↓ A little extra from this interview on Numberphile2: https://youtu.be/4qVM5CbKnF8 Kit Yates website: https://kityates.com More coronavirus content on Numberphile… The Coronavirus Curve with […]

Clever Solution To An Olympiad Question

Can you solve this tricky math problem? Thanks to Asad for the suggestion! Art of Problem Solving 2019 AIME Problem 3 (there are many solution methods) https://artofproblemsolving.com/wiki/index.php/2019_AIME_I_Problems/Problem_3 Subscribe: https://www.youtube.com/user/MindYourDecisions?sub_confirmation=1 Send me suggestions by email (address in video). I cannot reply to everyone but I consider all ideas! Like many YouTubers I use popular software to […]

Logic Test: What Is The 25th Number?

Can you solve this tricky question from the CSAT? Thanks to Sean from South Korea for the suggestion! Special thanks this month to: Mike Robertson, Michael Anvari, Kyle. 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 in video). I cannot reply to everyone but I consider all ideas! […]

What is the area? A nice problem from Singapore

Can you solve this challenging problem from the Mathematical Olympiad of Singapore? Thanks to Truong from Vietnam for the suggestion! Subscribe: https://www.youtube.com/user/MindYourDecisions?sub_confirmation=1 Send me suggestions by email (address in video). I cannot reply to everyone but I consider all ideas! Like many YouTubers I use popular software to prepare my videos. You can search for […]

A Simple Puzzle Stumps Many Adults. Can You Solve It?

“You have to solve this yourself, otherwise you won’t see how beautiful it is,” Lee Sallows. SoraNews24 Sinisterly simple math puzzle for elementary school kids stumps Japanese Twitter adults IT Media (Japanese) https://nlab.itmedia.co.jp/nl/articles/1706/15/news078.html Nob’s Number Puzzle (Nobuyuki Yoshigahara (芦ヶ原 伸之)) https://dodona.ugent.be/en/exercises/1191761379/ Subscribe: https://www.youtube.com/user/MindYourDecisions?sub_confirmation=1 Send me suggestions by email (address in video). I cannot reply to […]

Gabriel’s Horn Paradox – Numberphile

Featuring Tom Crawford. Check out Brilliant (get 20% off their premium service): https://brilliant.org/numberphile (sponsor) More links & stuff in full description below ↓↓↓ Extra footage from this interview: https://youtu.be/EsX9y0lKsZw Tom Crawford’s website, with links to his work and other outreach: https://tomrocksmaths.com More Tom Crawford videos on Numberphile: http://bit.ly/Crawford_Videos Infinity Paradoxes: https://youtu.be/dDl7g_2x74Q Vuvuzelas on Sixty Symbols […]

A lovely riddle

Can you solve this challenging Valentine’s Day problem? Thanks to Stéphane from Belgium for the suggestion! 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 for sales. (As an […]

A Radical Sum

This was asked to students in Indonesia. Can you figure it out? Special thanks this month to: Michael Anvari, Kyle, Mike Robertson. Thanks to all supporters on Patreon! Subscribe: https://www.youtube.com/user/MindYourDecisions?sub_confirmation=1 Send me suggestions by email (address in video). I cannot reply to everyone but I consider all ideas! Like many YouTubers I use popular software […]

A Curious Fact About Semicircles!

What fraction of the entire circle is shaded? Jobbings, A. (2011). The Mathematical Gazette https://www.cambridge.org/core/journals/mathematical-gazette/article/9564-two-semicircles-fill-half-a-circle/6365F0D492DF2E682E71A891C782CAF6 The chalice problem Azimuth Project (John Carlos Baez) Geometry Puzzles Folding proof by Greg Egan http://math.ucr.edu/home/baez/mathematical/semicircle_puzzle_egan.gif Cut The Knot https://www.cut-the-knot.org/proofs/Semicircles.shtml Subscribe: https://www.youtube.com/user/MindYourDecisions?sub_confirmation=1 Send me suggestions by email (address in video). I cannot reply to everyone but I consider all ideas! […]

Annoying Puzzles (and Cognitive Reflection Problems) – Numberphile

This video features Tim Harford. Check out Brilliant (get 20% off their premium service): https://brilliant.org/numberphile (sponsor) More links & stuff in full description below ↓↓↓ See an extra snippet from this interview on Numberphile2: https://youtu.be/1lwocqnBmVc Tim Harford website: https://timharford.com How to Make the World Add Up: https://amzn.to/3oBcDRx Or (different title in the US): The Data […]

What is the sum? The answer is “too” good!

Can you solve this challenging algebra problem? Source https://math.stackexchange.com/questions/3844738/if-x5-1-with-x-neq-1-then-find-value-of-fracx1x2-fracx21x4 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 […]

A proof that e is irrational – Numberphile

Professor Ed Copeland shows a proof by Joseph “Voldemort” Fourier that e is irrational. Check out episode sponsor http://KiwiCo.com/Numberphile for 50% off your first month of any subscription. The crates are great! More links & stuff in full description below ↓↓↓ Ed Copeland is a physics professor at the University of Nottingham. Check out more […]

What Is The Square’s Area?

Can you solve this delightful problem? Thanks to Elmer for the suggestion! Subscribe: https://www.youtube.com/user/MindYourDecisions?sub_confirmation=1 Send me suggestions by email (address in video). I cannot reply to everyone but I consider all ideas! Like many YouTubers I use popular software to prepare my videos. You can search for animation software tutorials on YouTube to learn how […]

Quasiperfect Numbers with Eric Lander – Numberphile

Eric Lander discusses how quasiperfect numbers gave him a start… More links & stuff in full description below ↓↓↓ This interview was filmed in 2015 but remained unedited and unpublished until now… The other main interview from that day (about “Basic Research”) can be found here: https://youtu.be/6gnsQjPCC78 The Westinghouse Science Talent Search has since become […]

WOW! A very satisfying answer

Thanks to Hrigved for the suggestion! 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 is time consuming […]

Triangles In A Row

Can you solve for the shaded area? 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 is time […]

The Drag Equation (Empire State Building v Eiffel Tower) – Numberphile

Tom Crawford discusses drag – then we drop the Empire State Building and Eiffel Tower into the ocean… Check out Brilliant (get 20% off their premium service): https://brilliant.org/numberphile (sponsor) More links & stuff in full description below ↓↓↓ Find out more about Tom Crawford: https://tomrocksmaths.com/about/ More Tom videos on Numberphile: http://bit.ly/Crawford_Videos Check out some raw […]

Simple puzzle everyone is talking about #Shorts

They say “You should be able to solve this,” but the internet can’t agree on the answer! What do you think? #Shorts MindYourDecisions poll results https://www.youtube.com/post/Ugzv_XryKGRUCCNDluN4AaABCQ The Moscow Puzzles (problem 37) by Boris A. Kordemsky, edited by Martin Gardner http://www.math.cmu.edu/~bkell/21110-2010s/algebra-puzzles.pdf https://www.doverpublications.com/mathsci/0718/d/270785_Easy_Answers.pdf Related memes https://www.physicsforums.com/threads/math-puzzle.477209/ https://knowyourmeme.com/forums/just-for-fun/topics/14038-you-really-should-be-able-to-solve-this Subscribe: https://www.youtube.com/user/MindYourDecisions?sub_confirmation=1 If you buy from the links below I […]

Solving MIT’s Father Son Riddle

MIT is one of the top ranked universities in the world. Can you solve this question from their 1876 admissions test? Source https://web.archive.org/web/20190703223047/https://libraries.mit.edu/archives/exhibits/exam-entrance1876/algebra1876.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 […]

5 Rectangles Puzzle

Thanks to Surjadi from Indonesia for the suggestion! Twitter Cshearer41 A square is split into five rectangles with equal areas. What’s the area of the square? pic.twitter.com/wtuEjxMASI — Catriona Agg (@Cshearer41) July 11, 2020 solution by @birkhofyan pic.twitter.com/3EIij7DjaU — Birkan Yıldız (@birkhofyan) July 11, 2020 Subscribe: https://www.youtube.com/user/MindYourDecisions?sub_confirmation=1 Send me suggestions by email (address in video). […]

Butterflies and Gyroids – Numberphile

Dr Sabetta Matsumoto discusses some of the mathematics of colour in nature, including butterfly wings and soap films. More links & stuff in full description below ↓↓↓ Dr Matsumoto’s group at Georgia Tech: http://matsumoto.gatech.edu And her Twitter: https://twitter.com/sabetta_ Previous video with Sabetta on Numberphile: https://youtu.be/0e5vzTsLh2s Brady looks at butterflies on Objectivity: https://youtu.be/lJWHppdupbI Numberphile is supported […]

Can You Solve Euler’s Egg Riddle?

Thanks to Francisco from Portugal for the suggestion! They say Euler asked this tricky algebra problem to his students. Reference Euler’s 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 […]