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  • Alright, we're gonna do some street maths

  • here in the outdoors,

  • which I've heard a lot about.

  • But first...

  • my shoe is untied.

  • So we need to fix that.

  • Now, most people would mess around doing some kind of complicated knot,

  • not me - I'm a mathematician.

  • I've got maths to do.

  • Grab the two sides, pass 'em over, boom! There's your knot.

  • Again, in slo-mo!

  • I'd heard about it, you know, on the maths circuit.

  • People would discuss the way that you tie your shoes, right?

  • And so – I know it's been around for a long time, I know it's been passed down

  • from mathematician to mathematician.

  • But I'm not familiar with the earliest case, and I have heard names assigned to it,

  • but I've not come across any one that particularly sticks.

  • I just call it "that brilliant way to tie your shoes."

  • (Brady) Be honest with me, is that how you do your shoes?

  • I do genuinely tie my shoes that way

  • I know I'm always talking about it

  • I literally tie my shoes that way.

  • Up to once a day.

  • Once it's done, it looks exactly the same, right?

  • So then people won't go, "That's an unusual knot," right?

  • But if they actually see it happening

  • It's like they've seen a magic trick, right?

  • It just blows their mind

  • They can't comprehend how a knot can happen so quickly.

  • But, I'm not startled; I'm a mathematician!

  • I know what I'm doing.

  • Okay, you go from completely undone, it starts the same way as a normal knot

  • You do your little foundation thing

  • Which in maths is called a trefoil

  • It has a minimum of three crossings in that particular knot

  • Now to tie the actual bow

  • You get one shoelace that's coming out the back

  • You fold it forward and you hold it on its way down

  • So it goes up over the loop and then down

  • This one curls back in the opposite direction

  • And again you hold it on the way down.

  • And then all you do is you take this one on the way down and put it under that loop

  • At the same time as taking this one and putting it under that loop

  • And then you swap them over to the other hands

  • And then you pull them tight, and that is your knot!

  • And with a little bit of practice,

  • Once you tighten it, hold them on the way down,

  • cross, pull, knot.

  • So the one that comes out the back, you fold it forward into a loop

  • And then you hold it on the way down

  • So it goes up and then on the way down you're grasping it

  • Same with this one except it goes back

  • So it starts at the front, curls back, hold it on the way down

  • Now you're gonna take this lace, put it under that loop

  • at the same time as taking this lace and putting it under that loop

  • So they go past each other

  • They swap hands, you pull it tight

  • And there's your knot.

  • People tie their shoelaces, they get one and they loop the other one around

  • and they pull it through, which is the normal way.

  • Although I've noticed, of course, Brady wears slip-ons.

  • (Brady) Why? What's wrong with them?

  • For those of us who have entered adulthood

  • We do it a long, complicated way.

  • But, the thing is, you end up with a knot that holds your shoe on.

  • That's the goal here

  • My shoelaces

  • Formed with what ordinary people would think is a knot

  • Now, nothing of this is a mathematical knot

  • Because it has loose ends

  • If it has loose ends, you can, in principle, untie it

  • And you can form a different knot.

Alright, we're gonna do some street maths

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靴紐を超高速で結ぶ方法 - Numberphile (Super-fast way to tie Shoelaces - Numberphile)

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    林宜悉 に公開 2021 年 01 月 14 日
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