# Matt Parker: Stand-up Maths Routine (about barcodes)

I'm very pleased that he agreed to come down to Hammersmith to give you a little bit of maths, so please welcome to the stage Matt Parker!
Alright.
Oh yeah. Okay.
Give me a cheer if you're ready to do some number theory!
That's so few audiences are up for number theory the comedy store one of them
I've checked, but we are actually going to do some number theory. My name is Matt I am a mathematician or
number Ninja and I'm
If you're laughing at that you're in for a treat in a moment
I'm here because not only can you not do science without maths, but you couldn't even have a science show
Without numbers in fact our modern civilization wouldn't be possible without number patterns
This is kind of the numbers of universe section
And to start that we are actually going to do some maths so could everyone who bought a calculator with them get that out now
Oh come on. This is your chance to shine nerds
Come on
Really sir don't get my hopes up
Are you disposing of your chewing gum?
I've lost it. Are you getting a calculator?
you, of, okay
calculator or universal Turing machine
Could you switch your iphone in calculator mode and could you put any four-digit number you fancy in?
What I want you to do sir is to multiply that by nine and hit equals and we're going to dispense a microphone for you
You are doing this, right?
You're not going to believe how this show is starting.
Have you got a four or five digit answer on your phone man?
Five digit, okay. Here's what we're going to do
Have we got a mic for this poor man?
Okay, you're going to have to yell really loud. I'm going to get you to read out the first four digits slowly
I'll say yep after each one, and I'll predict the final fifth digit if I get it correct
Can you shout yes very, very loudly? Are you ready?
Here we go, here we go. You're about to be amplified guy in the green
Well the guy who stopped it
He looks mildly more nervous now okay? What's the first a digit sir?
Four. To keep persist with the microphone.
Four. Hey!
There just one four okay. Four. Yep, three three seven yep three
Last digit is a one.
Correct.
Don't patronize me.
Did you feel that wave of disappointment just come crashing down? It's because there is a fairly straightforward master
it's not
Alarmingly difficult all I'm doing is adding the digits as you call them out and any
Multiple of nine if you add the digits the answer is another multiple of nine
Not alarmingly difficult, so let's let's amp this one up a notch, right?
And so I give you those of you who are unimpressed this. Now.
What
Not the CD the barcode
Had you worried for a second there, though
The only reason I have this CD right I listen to with all the dangerous high frequencies removed as a kind of way
inoculating myself against his tunes.
It is a fever going around town
What we're going to do with the-actually is anyone
Close to smilers over here got a product like a bottle of water or chewing gum or something you've purchased
Which has a okay miss has got a bottle of water. Can you pass the mic down to her?
Okay miss what you're going to do very similar to before is read the digits out one and time very slowly
I will predict the last digit. Before you start
Can you see the numbers here start just to the left of the line? Do you all start just to the left or underneath?
Have you got a barcode?
You're gonna have to invest in some actual words.
It starts with a letter
What? It starts with a letter. Okay. Could we get a different product there?
If you can't recognize numbers I've lost an awful lot of confidence.
Has anyone else- I've only got a finite amount of time here- got, okay. Yes, right have you got a barcode with numbers
Yes, Brilliant. Good, good. Does the first number start just to the left or underneath. It's just to the left. Brilliant, okay?
Here's what you're gonna do. You're going to read out those digits to me very slowly
I'll say yep after each one and don't tell me the last one. I'll predict it you shout "yes"! Everyone will go suitably wild
Five. Oh, okay five. Yep. Yep. Zero. Yep. One. Yep. Two. Zero. Woah woah woah woah
Okay, pick it up. Okay from, from five. Oh wait.
No after two.
Five.
Okay that's after the zero, right? Okay yeah good yeah.
Eight.
Yep. Zero. Yep. Zero. Yep. Three.
Yep. Zero. Yep. Zero. Yep. Last digit is a six.
Yeah.
Now I'm using a different pattern this time and it is a much more difficult pattern
If the front row was the barcode what I need to do is memorize every second digit as it's called out add
them together and then go back and add to get the
in-between digits as a second totals if you then multiply the first total by 3 add to
the second total the answer for a barcode if there are no letters
Always be a multiple of 10 and the reason that works is because of the last digit you sir
The rest of the barcode is like the product number and your what's called a redundant piece of information
Since you seem to call someone your you're the link click the bar
You don't actually do anything
But you're required to make the system work
And the reason you're there is wherever you scan a barcode the cash register performs that check to make sure there were no mistakes
The problem is if you detect a mistake you, you can see that something's gone wrong
But you can't do anything about it again. You're the nuclear bomb
Where's that first I could recreate the missing information in we were multiplying by nine, and when you send any information
You use more complicated versions of that pack in fact whenever you send a text message
your phone takes what you type in takes it as
Numbers puts it in a grid there's an extra digit for every single row an extra one for every single column splits
into sections and does a third mathematical pattern and converts it into
Well basically a Sudoku.
And so maybe you send a text message
It's sent as a complete sudoku
and if the receiving phone gets it and there are huge bits of information missing it can use the patterns to
Recreate and some of you are probably already doing this
To recreate all the missing information and without that kind of robust data transfer our modern society simply wouldn't be possible
Which is why that is my all-time second favorite use for Sudoku?
my all-time
Favorite use I do recommend this the next time you're on a train and it's really crowded everyone's around you get a paper out flip through the Sudoku
Just start filling in random numbers
Like you care. It really pisses everyone else
If you get someone hooked, right?
Put in a whole row of sevens
Put a twelve in that square. You guys have been lovely. Thank you very much