Thanks to Eric from Miami for suggesting this problem and sending a solution! The diagram shows a quadrilateral ABCD with the values for some angles and the length of AB. Can you figure out the area of ABCD? 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 My blog post for this video https://wp.me/p6aMk-85A

Tadashi Tokieda cuts various combinations of loops and Mobius loops – with surprising results. More links & stuff in full description below ↓↓↓ Part 2: https://youtu.be/mh3eMt09EAs And more: http://bit.ly/tadashi_vids 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

Can you measure exactly 4 gallons from jugs of 3 gallons and 5 gallons? This problem is featured in the movie “Die Hard With A Vengeance.” Here is the scene from the movie: https://www.youtube.com/watch?v=BVtQNK_ZUJg 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

Tadashi explores a special set of dice… And has a powerful lesson. More links & stuff in full description below ↓↓↓ Subscribe to Numberphile: http://bit.ly/Numberphile_Sub More dice videos: http://bit.ly/Dice_Videos Playlist of Tadashi Tokieda videos: http://bit.ly/tadashi_vids Want to buy some dice like this – our friends at Maths Gear have some: http://bit.ly/MathsGearDice Discuss this video on

This simple problem for kids is sure to stump some adults. Can you figure out the height of the table? Problem adapted from #quiz Here is a math word problem from a Chinese elementary school student's homework. Have a try to figure it out! Leave your answer in the comment. pic.twitter.com/kOlydqNDQO — China Focus (@China__Focus)

The Prime Number Theorem shows that primes are like weeds, popping up everywhere! Dr James Grime explains — Little bit extra cut from this video: http://youtu.be/TMRZYSQGAcw More links & stuff in full description below ↓↓↓ Our prime number video collection: http://bit.ly/primevids Follow James on Twitter at: https://twitter.com/jamesgrime NUMBERPHILE Website: http://www.numberphile.com/ Numberphile on Facebook: http://www.facebook.com/numberphile Numberphile

Thanks to Omer from Israel for suggesting this type of puzzle! Three friends rotate playing 1-on-1 basketball games. If A played 8 games, B played 11 games, and C played 15 games, who lost the 4th game? It seems impossible but you can logically figure it out! My blog post for this video https://wp.me/p6aMk-84r Sources

Tadashi’s back (for the final video in this mini series) demonstrating the Kendama and some angular momentum. More links & stuff in full description below ↓↓↓ Tadashi Tokieda will be back on Numberphile soon. Here’s a playlist of his videos: http://bit.ly/tadashi_vids Kendama also known as bilboquet or boliche or bolero. Video by Brady Haran and

You spin a wheel and it randomly lands on $1, $2, or END. If you land on $1 or $2, you bank the money and spin the wheel again. You keep spinning until you land on END, at which point you cash out the money you banked. How much do you expect to win on

Beautiful Dragon Curves, Fractals and Jurassic Park. Featuring Rob Eastaway. More links & stuff in full description below ↓↓↓ Rob’s website: http://www.robeastaway.com/ Thanks to Matthew Ward and Faraz Barzideh who helped Brady out with some curves! The book Jurassic Park is by the late Michael Crichton. NUMBERPHILE Website: http://www.numberphile.com/ Numberphile on Facebook: http://www.facebook.com/numberphile Numberphile tweets:

Ultimate Tic Tac Toe, also known as Nine Board Tic Tac Toe, is an interesting variation on the classic game. The board is composed of a 3×3 grid of Big Squares. Inside of each Big Square is another 3×3 grid, so there are 9 Small Squares inside each Big Square. The position you play in

Dr Tony Padilla’s unique (and low budget) twist on the Buffon’s Needle experiment to learn the true value of Pi. More links & stuff in full description below ↓↓↓ OUR PI VIDEOS — ALEX BELLOS AND ROGER DISCUSS ITS HISTORY BOUNCING BALLS AND A STRANGE PROPERTY MATCHES HELP FIND PI THE SOUND OF PI NUMBERPHILE

A calculus problem went viral! Some major websites are reporting that students at a university in China had to solve this for the WiFi password in a dining hall. This is actually a pretty fun calculus problem. Watch the video for its solution! Sources http://tech.ifeng.com/a/20180907/45156013_0.shtml http://www.dailymail.co.uk/news/article-6142997/Chinese-university-canteen-makes-students-answer-calculus-question-unlock-access-Wi-Fi.html https://www.cnet.com/news/wi-fi-access-only-granted-to-students-in-china-after-they-solve-a-puzzle/ https://en.wikipedia.org/wiki/Zu_Chongzhi https://www.ict4us.com/r.kuijt/en_pi_onthouden.htm My blog post for this video

Part Three of Golden Ratio Trilogy Why the Lucas Numbers are better than the Fibonacci Sequence. More links & stuff in full description below ↓↓↓ Matt’s signed book (& extra goodies): http://bit.ly/Matt_Signed Amazon (UK): http://bit.ly/Matt_4D_UK Amazon (US): http://bit.ly/Matt_4D_US All links to videos in this four-part trilogy: Brady Numbers: http://youtu.be/D8ntDpBm6Ok Proof: http://youtu.be/dTWKKvlZB08 Lucas Numbers: http://youtu.be/PeUbRXnbmms Extra

This clock displays time accurately like any other 12 hour clock. But this clock has no numbers, and the clock has been rotated out of position. Based on the position of the hour and minute hands, what time is it? This problem was asked to primary school students in China, can you figure it out?

Main video is at: http://youtu.be/seUU2bZtfgM This is some extra stuff from Simon Pampena we didn’t use in the first video! More links & stuff in full description below ↓↓↓ 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/ Brady’s latest videos across

Warren Buffett once challenged Bill Gates to a dice game similar to this one. How would you play the game? Blog post (text explanation) http://wp.me/p6aMk-4ro Source The dice numbers and the story are described at Microsoft Research’s website for non-transitive dice http://research.microsoft.com/en-us/projects/dice/ If you like my videos, you can support me at Patreon: https://www.patreon.com/mindyourdecisions Connect

Not all jokes are in base 10… More links & stuff in full description below ↓↓↓ With thanks to Audible – http://www.audible.com/numberphile (book details below) More jokes explained at: http://youtu.be/JJQWtGm3eIs Animation by by Pete McPartlan – http://www.petemcpartlan.co.uk Explanations by Matt Parker – http://www.standupmaths.com This video was posted during YouTube Comedy Week: http://yt.be/comedyweek Leave more joke

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

Patreon: http://www.patreon.com/numberphile More links & stuff in full description below ↓↓↓ Tony Padilla is an associate professor of physics at the University of Nottingham. Here he discusses the zeta function and Apéry’s Constant. More Tony videos: http://bit.ly/Padilla_Numberphile Tony’s Tweet: https://twitter.com/DrTonyPadilla/status/828527018081918976 Roger Apéry pics courtesy of François Apéry Numberphile is supported by the Mathematical Sciences Research

Did you know some math problems were used to discriminate against groups of people? This is one such problem, and it stumped me! But it has an unbelievably elegant solution. Take any equilateral triangle and pick a random point inside the triangle. Draw from each vertex a line to the random point. Two of the

Cliff Stoll is passionate about Klein Bottles. More links & stuff in full description below ↓↓↓ Don’t miss the video about how he uses a robot to store 1,000 bottles UNDER his house… https://youtu.be/-k3mVnRlQLU More videos on Klein Bottles: http://bit.ly/KleinBottles ACME Klein Bottles: http://bit.ly/ACME_Klein Support us on Patreon: http://www.patreon.com/numberphile NUMBERPHILE Website: http://www.numberphile.com/ Numberphile on Facebook:

What is 7×8? This video teaches how you can use your hands to multiply two numbers between 6 and 10 using your fingers. Here’s the reason the method works: https://www.youtube.com/watch?v=eEao6-F7fz8 If you like my videos, you can support me at Patreon: https://www.patreon.com/mindyourdecisions Connect on social media. I update each site when I have a new

Graham’s Number (Numberphile T-Shirt): http://bit.ly/Grahams_T-Shirt More links & stuff in full description below ↓↓↓ The magnitude of Graham’s Number is difficult to fathom – Ron Graham himself attempts to explain. WHAT IS the number: http://youtu.be/HX8bihEe3nA Extra footage: http://youtu.be/rGWuimr5CGQ Our original Graham’s Number video: http://youtu.be/XTeJ64KD5cg Any errors in this video are mine (Brady’s) in editing… For