You can enter the submittable part of the puzzle at https://www.think-maths.co.uk/maths-puzzles

I wasn’t kidding, this is where almost all of my t-shirts come from:

Mens

Thanks to my co-host Matt Parker.

Huge thanks as always to my principle channel sponsor Jane Street!

https://www.janestreet.com/

And much thanks to Deanna and Oliver who are now helping us run Matt Parker’s Maths Puzzles. Deanna is making the massive sacrifice of giving up her place near the top of the leader board!

CORRECTIONS

– Nothing yet. Let me know if you spot anything!

Thanks to my Patreon supports who do support these videos and make them possible. Here is a random subset:

Sarah Gerweck

Baadrix

Derek Chandler

Fernando Gaete F.

Brandon

Alan Flett

Richard Fourie

Elaine Hewitson

Ahmed Hindawi

Alan McNea

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Filming and editing by Matt Parker and Matt Parker

Music by Howard Carter

Design by Simon Wright

MATT PARKER: Stand-up Mathematician

Website: http://standupmaths.com/

US book: https://www.penguinrandomhouse.com/books/610964/humble-pi-by-matt-parker/

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source

That was a genuinely impressive level of coordination

Your writing in South Park is funnier.

The answer is 15 and here is a combination of moves that will guarantee it:

121312141213121

This is because there are two ways for each of the four cards to be facing, meaning there are 16 possible combinations. If you turn over the first card, you can reach a new combination. By turning over the second card then the first card, you can reach both of your two initial combinations except with the second card facing the opposite way. Then when you flip the third card over and then one, two and one in that order, you'll reach the first four combinations except now with the third card turned etc… This will cover every single possible permutation and guarantees all the cards will face down within 15 or less moves. Pretty EZ.

step 1 of my solution is to uncover your eyes

As a video editor, I giggled when I got to 2:32. Well played, sir.

Editors: Did you use only one chair? Well it doesn't matter

0.0 how do you pass yourself the cards??????????? 2:32

"[Y]ou can play with a friend, although at the moment I'm not allowed to have…"

Friends? That seems like a pretty harsh law….

me when everyone leaves the house finally

Good work passing the cards from the first to the second Matt.

When everyone forgets about the card trick and wonders how Matt was able to make the video xD

amazing editing

123412312143214

@2:33 – Wait a minute, that was clever! 😂🤔

Havnt watched the end yet, i think the answer is 15 which can be achieved with the pattern

434243414342434

Since it's just a binary counter I suppose it would take a maximum of 15 tries before hitting the right sequence!? I would be very curious if there is some smarter way to sort it tho. Since it's an old video I will go try and look up the answer 🙂

So… Isn't the answer 2^n?

Also, I need to see a 3x or 4x Matt video, his timing is actually quite impressive.

Not gonna lie, the 2:30 hand-off trick was pretty impressive.

Matt got rid of the wrong Matt.

I was thinking binary. if you count up in binary then the max number of turns is 2^4=16 moves. You can choose randomly which ones are each power of 2 also since tbh order doesn't matter

@2:55 Okay, well, the obvious and painstaking solution is to iterate over every combination of flipped or not from the initial.

i.e. Flip 1, flip 1, flip 2, then 1, flip 1 and 2, flip 3, etc. Basically, by flipping individual bits count to 2^N – 1 where N is the number of cards.

I don't think you can do any better without psychology.

If you cross your eyes, you can see him in stereoscopic 3D!

woah he must have scripted it nicely, passing the cards would be very difficult with cuts

%y question is: which Parker was filmed first?

Submitting my solution here because I'm late. Spoilers.

What's essentially happening is I've got a four bit 'answer' starting with all zeros, I get to change one bit per turn, and after every turn my answer is compared with the solution to see if it matches. So, I just need to loop through all of the possible answers, only switching one bit at a time. Luckily for me, that's exactly what the Gray code is. Answer: 1,2,1,3,1,2,1,4,1,2,1,3,1,2,1

I award myself full points because I know that's the correct solution, but I'll deduct points for not knowing the Gray code well enough to reproduce that simple pattern from memory and for an overdue submission.

I must congratulate you Matt, that was brilliant editing.

Out of interest, which Matt was filmed first? (So which one was cheating for their answer?)

Matt, tell Matt not to touch his face with his hands, it's unsanitary 😮