Number Sticks - Numberphile

[@MattMcIrvin]

Interesting to think about why they specifically chose the _third_ number on each stick to be the odd one out. Probably because that's the position where your audience is least likely to pay attention to what's written there.

[@prithusharma2559]

Matt McIrvin lol it's not that

[@rlamacraft]

Prithu Sharma so what is it?

[@davidbouldin3326]

I'm assuming, then, you can add more and more sticks and it works the same. However, what you gain in mathematical impressiveness, you risk in being exposed. The longer the number, the more likely they are to notice the alignment with the third row.

[@mow184]

David Bouldin I'm thinking no...? Because there's only a limited number of ways in which you can present 18 as the sum of three other single-digit numbers?

[@dlevi67]

+mow184 you could have the same set of sticks - even the same stick - used n times, the maths would still work, but the risk of someone noticing increases. That's one of the reasons why the "back" trick works well: it takes away the attention from the numbers at the front.

[@jwolfe01234]

If my calculations are correct, you could have 52 sticks that perform both of the tricks in the video and (a) don't repeat a digit in a given number (b) don't use the digits 0 or 1, and (c) don't use the same 4 digit number twice. Rather than make a number that long, you could just put them all in a bucket and have someone choose 3-5 of them.

[@givememore4free]

I ACTUALLY UNDERSTOOD AN EPISODE OF NUMBERPHILE!!!! I feel smart

[@aloknight3656]

Same!

[@Triantalex]

??

[@JoshGroach]

I hope the next video is about Parker Sticks.

[@woud3404]

Parker sticks: 19 190 1900 19000 190000 _______ 211109 Substract 1 from the last number, and add 1 to the rest UNLESS the last number is 0, then you add 0 to the second to last number. There you go, parker sticks.

[@dirm12]

@C Almost always.

[@friedmanism2]

The sound of those sticks clicking together is perfect ASMR material

[@custersword7746]

A lovely little magic trick because the numbers are not all just shuffled with the same result for two different combinations! Also love the Mario fire flower shirt!

[@alexisglennespina8471]

I have the exact same calculator as the one they used in the video. Amazing!!!

[@hallfiry]

It's a bit less transparent if the three digits don't add up to 18, but instead 17, so you have to subtract 1 from each digit and then subtract 3 from the whole number. That way the exact digits won't be visible on the sticks themselves.

[@M3NTALMAGIC]

there was a version of this method manufactured a while back

[@KauanRMKlein]

Really cool! I wanna buy those!

[@masansr]

What I found interesting is when Brady worked the calculator, he first searched for "8" and "7" on the bottom (like you'd do on phones).

[@KasabianFan44]

I always tend to do the opposite: I look for a 7 or 8 in the top row on a phone because that’s where they are on a calculator 😂

[@alaaazzam100]

Thank you. It took me a lot of research to get to your videos

[@macronencer]

Interesting fact: there are 6144 different ways to arrange the rods, but only 2880 different totals, ranging from 22232 to 29984. I love Microsoft Excel!

[@Lashb1ade]

I believe this should work if the numbers add to 27 (this would need a stick of height 5+; otherwise you just have three 9s). You will need to add and subtract a 3 for the ends. Extend for 36, et.c. until it gets more complicated after 81.

[@thepuzzledmagician]

Another way to understand this trick: imagine combining the 3 rows of numbers into 2 rows of 9,999. When added together 9,999 + 9,999 = 20,000 minus 2...as you saw in the video. This same effect can be done with paper and pencil. The only real difference is that you will have 5 rows of numbers instead of 4. You and the volunteer take turns writing random 4 digit numbers. Each time you write a number it needs to be the "nines complement" of the volunteer's number. In other words, your number when added to their number needs to total 9,999. Do this twice and then add a 5th line of numbers that you chose ahead of time. Because you already knew these numbers you were also able to write a prediction of the total of all 5 rows. To make your prediction just put a 2 in front of that number and subtract 2 from the last digit. Hope that makes sense.

[@ElusiveCube]

here is one similar; have two digit number, say.31 and reverse the order when subtracting so 31-13 = 18, so 81 -18 = 63-36=27 ,so 72-27 = 45 so 54-45= 9, to do this 9 will always be the answer.

[@heyandy889]

thank you katie and brady

[@XWurstbrotX]

You should be able to do that with more Sticks aswell, right?

[@AbramSF]

XWurstbrotX It’s pretty cool. I could tell just by looking at them that this would be the solution to the puzzle. So they could definitely use some improvement.

[@filipsperl]

with more sticks, the trick might become too obvious

[@3dayblackout]

+Peter Rabitt very funny...

[@catman64k]

+Peter Rabitt no one is written as two words or with a hyphen in between =)

[@dlevi67]

+catman64k whoosshhh....

[@eashanshenai4980]

Katie 'STICK'els right? Nope?.... Ok i'll leave now

[@musataz]

Brady's typing speed tho....

[@NoNameAtAll2]

Well he has heavy camera in the other hand

[@custersword7746]

I believe the calculator was suboptimal

[@tomtrask_YT]

It gives you time to do the sum in your head

[@vapzach9640]

Custersword But the calculator has the revolutionary ergonomic ARC™ design, as reviewed by Matt Parker in a calculator unboxing video.

[@Vulcapyro]

listen to hello internet

[@MrRyanroberson1]

a more advanced form: make the fourth number even when the sum of that stick is 18 and odd when it's 17, and using that if you find the 4th is odd you decrement the third of that stick.

[@matthewlurton4168]

The answer to the question at the end is you'd expect the program to flag non-spam as spam around 2/3rds of the time. It's a pretty classic example of Bayes' Probability Theorem. The Probability of event A occurring given event B is equal to the probability of event B occurring given Event A divided by the unconditional probability of event B, times the unconditional probability of event A. Uncovering the unconditional probability of event B is generally the trickiest part, because you need both the probability of B occurring given A plus the probability of B occurring given that A does not occur.

[@InvadersDie]

actually, it does not matter if he recieves 100% spam or 1% spam, the filter gives each email marked as spam a probability of being spam 98% of the time.

[@matthewlurton4168]

That's not correct. Even though the chance of any given report of spam being false is only 2%, the chance of any given email actually BEING spam is even more remote, at 1%. Because it's such a rare event, even the high certainty of the spam blocker doesn't cancel out the improbability of any particular email being spam, thus the 1/3rd answer.

[@8bit_pineapple]

Ehh, I don't think you even need to use Bayes theorem. I just thought, in 100 emails you'd expect 99 real mail, 1 spam email. Of the 99 real, you expect 2% to be marked incorrectly as spam, so you'd expect just under 2 emails to be incorrectly marked as spam. Whereas for the 1 real spam email the expected number of spam mails to be correctly marked is 0.98. So, in general more real emails are being marked as spam as spam emails.

[@InvadersDie]

We already know the email was marked as spam though. so it's 98% likely to be spam.

[@InvadersDie]

The way I see it is, if the spam filter is 98% accurate then 98% of the spam folder's contents has to be spam. If it was a "not-spam" filter with 98% accuracy then 2% of the inbox would be spam.

[@murphymcbride6863]

I coach a UIL Number Sense team. 4th and 5th grade. They think this is soooo cool. We're making our own. :)

[@jessejamesmcguire]

Thanks for exposing magic to Laymen.

[@campshay19]

cant wait to see on reddit where a Tim will get super excited about the nail and gear being in the background omg no way

[@very_trees]

I've used these with Primary school kids! I knew this one!! Yay :)

[@Norgust]

Note that there is no "1" on the third row. That would make the calculation a bit harder :-)

[@lucasng4712]

Why?

[@ZipplyZane]

Because, if the 1 is in the rightmost column, subtracting 2 would require borrowing from the previous digit.

[@lisamariefan]

An interesting caveat that is easy enough to notice is that the third column must always be 2 or greater.

[@sandeepvk]

Excellent - Nifty little trick :)

[@Tatiana-jt9hd]

Yes I finally came here within 1h!! As amazing (and sometimes complicated) as ever.

[@arturgrygierczyk5636]

- 'Would you like to see a magic trick?' - 'No.' End of video

[@abiduzzaman8854]

WHERE IS JAMES GRIME!!!!!!!

[@JorgetePanete]

Abid Zaman you forgot the question mark

[@abiduzzaman8854]

oops

[@ChrisLuigiTails]

MATT PARKER!!!!!!!

[@abiduzzaman8854]

ChrisLuigiTails yeah!!!!!!!

[@danielchequer5842]

WHAT ABOUT CLIFF STOLLLLLLLLL!!! I WANT MORE KLEIN BOTTLE FETISH GUY

[@richardo.maxwell6262]

I'm Korean, and I want Koreans to know your channel. I want to show your interesting videos to Koreans. Can I make a Korean subtitle of your video?

[@RedRad1990]

Anyone else thought the name "Mental Logs" meant there will be logarithms involved?

[@MichaelPechner]

Found these on ebay for $18. On amazon the seller wanted $65. The amazon UK sellers will not ship to the US.

[@aloknight3656]

I want some now

[@macronencer]

Magnificent! I've never clicked an Amazon affiliate link so fast. I HAD to have a set of those!

[@buckryan1173]

I'm buying these! I am going to trick my math professor.

[@MagicMagnel]

hello. Do you know if exist any version that also includes zeros and ones? Thank you

[@zixuan1630]

Wow, you calculator looks like a calculator in Calculator Unboxing #1.

[@Luigi90900]

Nice product placement for a calculator unboxing video. #ParkerCalculator

[@DemusPetrus]

Could you make a video about ternary computer system?

[@dailydols]

I also got a magic purple rod....

[@MisterAppleEsq]

That pitch at the end was Brilliant.

[@mathewwhite7299]

do one on the number 89

[@peterfireflylund]

Do Napier's bones!

[@aldadebater]

Same these sticks can't be shipped to the US...

[@RichardDominguezTheMagicIsReal]

so if I wanted to make them, the numbers in the 3rd position can be any number so long as the other 3 numbers total 18, is that right ?

[@Shit_I_Missed.]

Yes, I think there are 510 combinations of four numbers that will work for this. Basically just work out all of the different sums of 3 integers to 18, and then multiply that by 10

[@AidanRatnage]

So could you do this with any number of these number sticks/mental logs or do they have different totals other than 18?

[@thydimov9909]

nah if you have 2x 4 logs i think you can still do it noone would want to make them different

[@AidanRatnage]

You could definitely do that.

[@abhijithasok4314]

Why does π make the whole world look weird, why can't i calculate the area of a circle or anything about anything remotely related to a circle to a definite finite number, when ever I see π i slip into a spiral of thought about who weird this number make the whole universe look like. Is π the sum total of all chaos of the universe. Or am i just high Plzz make a video on the weirdness of the universe because of π

[@13263846]

sound like kinda of dimension magic trick.

[@iainwalker8701]

Nice look, especially the earings

[@alfonsoeducador]

Oh yeah!!👏

[@eddysparks9093]

Wow! What a bunch of winners. No one wants to think. This is not a magic channel. This is a clever way to understand numbers and their relationships with each other. It creates fun for kids and makes them want to learn and be problem solvers. It would be cool if they made binary ones. Cool tool!

[@adolfoartigas3249]

I tried purchasing the Mental Math logs on Amazon but the company doesn't deliver to the States. :(

[@bijoyazizah9777]

Hi bos

[@deadlypyre]

No International Pie Day Special this year ? :-/

[@robertlozyniak3661]

The problem with this is you might end up convincing people that you're better at arithmetic than you really are.

[@ljm37]

Robert Lozyniak I did this once and now people keep asking me to balance their checkbook

[@andresxj1]

So what's the answer to the spam problem??

[@Cellkist]

Andy Arteaga I believe the point is to go find out

[@givememore4free]

Answer is to fry it up

[@JohnRoads]

The email is not spam.

[@tofus_21]

in order for the program to flag a mail as spam it either is spam and it was correct or it isn't and it was false. possibility 1 (spam): 0,01 * 0,98 = 0,0098 possibility 2 (no spam): 0,99 * 0,02 = 0,0198 so the chance that the mail is no spam is almost twice as big as the chance that it is in fact spam.

[@carterwood4197]

My reasoning was: One in a hundred is spam, but two in a hundred flagged as spam are false positives, so it's twice as likely that it's not spam. I suppose that's a little simplistic compared to actually calculating the probabilities (as Steffen Hinderink did), but I still got the right answer.

[@ButtleBeard]

I love (and also have) your shirt!

[@MCLegoboy]

You wanna buy some number sticks?

[@vapzach9640]

MCLegoboy You don't want to sell me number sticks.

[@theoreticalstranger4339]

You want to go home and rethink your life

[@TheBlundert4ker]

Don't try it

[@benjaminlam3514]

It's over Anakin! My position on the Y-axis is of greater value than yours!

Brilliant really is a great website though.

[@TGC40401]

After this comment, i will have comment every type of comment imaginable. I have truly ascended.

[@rudemanthony]

This is a fun way to cast out 9s

[@Radispi]

"Oh, look! A snowman!" xD

[@TimSter15]

Wait hang on... Canon make calculators??

[@honkatatonka]

The first sentence hit an instant Joker moment.

[@Max_Flashheart]

Those are loaded logs!

[@Charles-sj7zl]

Her hair is cool

[@yourlocalclosetedgaybestie3165]

Wow.. those are awesome. Can that happen with more sticks like 8 or 9?? I imagine it would but not sure...

[@MichaelDarrow-tr1mn]

it would

[@maxcap60]

is Banksy selling shirts?

[@munnadas9713]

314 people 3.14 pi

[@dxutube]

Awesome purple

[@masonchung2360]

*ALWAYS*

[@therabbits69]

This reminds me of the math trick James Grime did.

[@videojeroki]

I have the same tee-shirt! ;)

[@rohanmandayam847]

Wasn't there a similar numberphile video a long time ago?

[@oranj.h]

Did slightly wonder if this was going to be a video about Cuisenaire rods.

[@MrFireInTheDisco]

That hunt and peck calculator.

[@bijoyazizah9777]

17/02/2021 give me bos

[@blueandgreenslacks]

Watching this on the toilet & I just dropped a mental log.🤓💩

[@eddysparks9093]

Did it have numbers on it? Like number 2?

[@tmfan3888]

why dun they have 1?

[@canpz]

301 view

[@matthewniles2817]

woo top 20

[@lachlanstewart9314]

Brady's ASMR Calculator

[@607]

The question at the end has important information missing, I think.

[@numberphile]

It’s still question of the week. Go check it out?!

[@BlokenArrow]

I think it’s a P(A|B) - P(A) = P(B|A) thing. If the spam filter is 98% accurate, then 2% of non spam and 98% of spam get caught. Depending on whether you have a work email (which means almost all email is not spam) or a hotmail (which means almost all email IS spam), you might get a different answer.

[@607]

BlokenArrow Interesting, but I was actually talking about the medium difficulty question. It doesn't specify anything about the amount of snow used, is the problem. If everyone uses the same amount of snow, the puzzle is solvable, I suppose, but otherwise it doesn't make much sense.

[@lodewijk.]

haha 69

[@Wowthatsfail]

d00dle dude that's very offensive to say to a feminist!

[@Tatiana-jt9hd]

thats not funny!!

[@lodewijk.]

Anna Walker yes I know

[@kneedeepinclunge69]

you could only expect this level of high-brow nuanced comedy as the top comment on a numberphile video

[@sadhlife]

69th like thank me later

[@villagernutcracker3326]

"minusing 2"

[@zacgarcia9082]

I cant order these im sad Why america why?

[@serkanMKose]

they're just sticks with numbers on them...

[@Cellkist]

Yeah I was just thinking that. You could make these yourself really quickly.

[@zacgarcia9082]

Huh...

[@lobrundell4264]

I thought you were saying you couldn't put them in order at first x)

[@Adowrath]

Matt would probably approve of that Calculator.

[@numberphile]

It's the one we used in an unboxing!!!

[@ludvercz]

"You could get away with using this in a maths department" - Matt Parker 2013

[@esotericVideos]

I'm going to make this pencil disappear...

[@rodkakarot2553]

Ohh come on this is not magic this is cheating

[@Bbonno]

So is all magic once you know how it works :p

[@ilangated]

Magic ain't real, it's all some trick

[@lagomoof]

"Any sufficiently advanced technology is indistinguishable from magic." -- Arthur C. Clarke

[@SC-zq6cu]

Lagraig O'Moof But these are just sticks with nos. on them though.

[@MattMcIrvin]

Magic is cheating plus showmanship.

[@HL-iw1du]

numba

[@shrimatkapoor2200]

This has come on scam school

[@hiddens2346]

How to troll someone: TIP #1 Read more

[@Okero97]

2251st!

[@two2mass]

Why would that one person dislike?!?

[@Tahgtahv]

Must be an English Major.

[@ireneofunes89]

Here is one possibility. The person is desperately bored and starved for attention. They look for videos that have very few dislikes, click dislike, and then check back later to see if anybody has acknowledged. You've encouraged them yet again. Well done.

[@goharawais5335]

Its 18 dislikes now, either the guy is desperate af and is making alts or its a cult

[@isaiahbathurst3844]

Lol he's a professional mathematician and doesn't even have a scientific calculator

[@RUBBER_BULLET]

Do death sticks.

[@M3NTALMAGIC]

there's a cooler, more evasive version of this effect.....fools most magicians and math geeks

[@M3NTALMAGIC]

@Robert Irwin 2 years sheesh------ya a chinese version has a more deceptive solution and just as easy.

[@fragbully542]

Ok so.... I watched like 10 seconds and. Hmmmm let's make a sum with RULES...... omg there's a pattern. Hmmmmmmmmm must be the rules.