The almost impossible chessboard puzzle
1,001,780
Published 2020-07-05
Thanks to Gordon' s Wine Bar for letting us film in their bar. Ha! It wasn't a dungeon, it was a wine bar all along! (An amazing wine bar at that; definitely visit it next time you're in London (and things are open again)). www.gordonswinebar.com/
Also: this was filmed back in February 2020 pre-coronavirus (at least before we knew about it). Which is why we're sat so close together and not wearing masks. And people are phoning a wine bar.
For those of you want it all, and you want it now, we've put the complete, unedited footage of Matt and Grant completing the puzzle scenario on Matt's second channel.
• Matt and Grant do the whole coin puzz...
We'll put the deleted footage on the Stand-up Maths patreon page: www.patreon.com/posts/39003911
Sorry the audio is a bit hit and miss. Matt's microphone dropped out for a bit so we tried to rescue the audio from Grant's lapel mic. With some success.
Puzzle as emailed by Grant to Matt:
Prisoner 1 walks in, sees a chessboard where each square has a coin on top, flipped either to heads or tails. The warden places the key under one of the squares, which prisoner 1 sees. Before he leaves, he must turn over one and only one coin. Prisoner 2 then walks in and is supposed to be able to figure out which squares the key is in just by looking at the arrangement of coins.
This is the website Matt mentioned with a full breakdown of the solution and interactive boards you can play with.
datagenetics.com/blog/december12014/index.html
CORRECTIONS:
- At 20:42 when I (Matt) said "You're now assigning a 64-dimension..." he meant to say "You're now assigning a 6-dimension...". But that is a moot point because Grant can visualise cubes in all dimension spaces with equal ease.
- At 24:20 I said Venn and Euler the wrong way around. No one tell Steve Mould!
- Let me know if you spot anything else.
Thanks again, as always, for Jane Street being my principal sponsor.
www.janestreet.com/
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Matt Langford
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Filming and editing by Alex Genn-Bash
Music by Howard Carter
Design by Simon Wright and Adam Robinson
MATT PARKER: Stand-up Mathematician
Website: standupmaths.com/
Maths book: wwwh.umble-pi.com/
Nerdy maths toys: mathsgear.co.uk/
All Comments (9)
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This was a blast, thanks for making it happen!
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"Mathematicians don't like […] losing, so they simply prove they can't win"
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It seems like this assumed that you know which side of the board is the top. Note: The chessboards I have owned don't have letters or numbers, so I hadn't assumed this one was labeled. It looks like the chessboard in this video is also unlabeled. People keep suggesting that the labels are a solution, so I thought it would be helpful to clarify (note added Sept 2021)
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Matt's channel has to have the weirdest watch time analytics. Everyone seems to watch like 4 mins of his videos... pauses it... then restarts it sometime between 5 seconds and 2 weeks later.
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Seeing 3Blue1Brown in person was slightly mind blowing. I always assumed him to be a disembodied voice.
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Warden: *rotates chessboard* *evil laugh*
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I came across this puzzle about 5 years ago when a colleague told me about it. Being a computer programmer I immediately turned to solving it using computing and worked it out after about 4 days. Wrote a little c program for it, and was very chuffed with myself. I told my girlfriend at the time and she wasn't that impressed.
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There is a dead pixel on your camera [void screams]
