The Birthday Paradox

How many people need to be in a room before there’s a 50% chance that two of them share the same birthday? Is it about 180, since that’s around half of 365? Is it only 100? The real answer is surprisingly much, much smaller.
If you have just 23 people in a room, the odds of whether two get presents on the same day is a coin flip. Get 50 people together and that shared-birthday probability skyrockets to 97%. A handful more and it’s a virtual statistical certainty.
Really? Yes, really! With the aid of tiny plastic babies and some mathematics, Kevin proves and visualizes this surprising veridical paradox.
*** LINKS ***
Birthday Attack Example In Hacking
• 359 Example of a Birth...
Birthday Attack Hash Collision
• Birthday Attack: Hash ...
Hashing Algorithms And Security - Computerphile
• Hashing Algorithms and...
Discussion On The Birthday Attack
• Discussion on The Birt...
The Birthday Attack
danielmiessler.com/study/birt...
***********
Vsauce2 Links
Twitter: / vsaucetwo
Facebook: / vsaucetwo
Hosted, Produced, And Edited by Kevin Lieber
Instagram: / kevlieber
Twitter: / kevinlieber
Website: kevinlieber.com
Research And Writing by Matthew Tabor
/ matthewktabor
Huge Thanks To Paula Lieber
www.etsy.com/shop/Craftality
Get Vsauce's favorite science and math toys delivered to your door!
www.curiositybox.com/
Select Music By Jake Chudnow: / jakechudnow
MY PODCAST -- THE CREATE UNKNOWN
/ thecreateunknown

[@Vsauce2]

Hey I just recently passed 4 million subscribers and just wanted to thank each and every one of you!!! Now if you'll excuse me I have a cup of babies to finish drinking.

[@bronsonsnip0r]

the bitdefender link is not working for me :(

[@PunishedSenp]

No problem, you deserve it

[@ukrolelo]

@@bronsonsnip0r me2

[@kumoriani]

You're pretty much the new Vsauce anyway, might as well drop that 2 and make it official

[@gamemak0r]

Hey if I'm born 1/1/1990 1AM GMT +13 and someone is born simultaneously in a different part of the world 31/12/1989 GMT -12 who is older?

[@thejesuschrist]

You could say my birthday is a paradox.

[@Greeezy]

Or is it a pair of docs? Hmmmm

[@HuskerFox]

Nice :)

[@kristianhoward2217]

:o Is jesus aeithies?

[@InfernoCatalyst]

Nah, just an illusion.

[@arnodiedrichs3371]

Yes, everyone get's pesents, except you.

[@mkaylaC1622]

I feel like I just learned everything and forgot everything at the same time

[@zebmiller510]

Welcome, good sir, to Vsauce

[@geraldbal7945]

damn my neurons just grew exponentially!

[@supplant9124]

School basically

[@el.tubenJr]

I watch to much stuff to keep up with it

[@gizmofn1957]

That what it's like taking acid

[@beepduck]

if you are in a room with 50 people, theres a pretty low chance that one of them will share your birthday, but a very high chance that at least two of the other people will have a shared birthday

[@rajveerkanojiya2985]

I understood it with the video but whoever can't they gotta look at this comment and now this reply cause YOU HAVING THE SAME BIRTHDAY AS THE OTHER PERSON AND BY IT I MEAN YOU HAVING SAME BIRTHDAY EXACT SAME SO THE 50% CHANCE WOULD STILL BE WHEN THERE WILL BE 182 BABIES BUT IN THIS VIDEO THEY ARE NOT TALKING ABOUT YOU SPECIFICALLY THEY ARE TALKING ABOUT ANY 2 PEOPLE OUT OF THOSE 23 I HOPE YOU UNDERSTOOD

[@ki_yoon]

Actually, the probability in that case is about 12%

[@zaug1561]

@@ki_yoon 365/50=7.3.....100/7.3=13.6986..... The probability is 13.6986% one of those 50 people will share your birthday. Edit: Disregard this, I'm an idiot.

[@ki_yoon]

@@zaug1561 The correct method of calculation is to compute the opposite case and subtract it from 1. When there are 50 people, the probability that everyone's birthday is different from you is (364/365)^50 ≒ 87.18%, so the probability that there's someone who has the same birthday as you is about 12.82%

[@zaug1561]

@@ki_yoon The chance of 1 person having the same birthday as you is 1 in 365. That seems obvious enough. So the chances of 50 people having the same birthday as you would be 50 in 365. It's that simple. Edit: Disregard this, I'm an idiot.

[@dimitristripakis7364]

I am a highschool teacher and this explains why, when anyone has their birthday, someone else will say "me/my dad/mom/sister also has a birthday today". That is, if you count 23 students in class plus 3 relatives at home each, gives a total of about 90 people and the chance is close to 100%. Makes sense after all!

[@Checkmate777]

I still don’t get why it’s a 50% chance of 23 people having the same birthday.

[@clarazegarelli5861]

@@Checkmate777 Is not too intuitive, and he does not explain well in my opinion.

[@KingCaleb55]

@@Checkmate777when I first thought about it, I was thinking you choose 2 random people and it’s a 50% chance of them having the same birthday, that’s wrong. He’s saying that 23 people in a room pair up with each other to see if they have the same birthday, that’s 253 pairs which greatly increases the probability. Now you take 253 (number of pairs) times 1/365 (the chance of any pair having the same birthday.) that equals around 69%. But that means that with any more than 365 pairs the chance surpasses 100% which isn’t possible so the chance decreases to about 50%. Hope that helps.

[@vollkornkeks9177]

​@@KingCaleb55your math is wrong

[@JamieEmmons]

how does 23 people equal 253 pairs@@KingCaleb55

[@maverick-rs]

Teacher: I have a math problem. Let's say you have 23 babies- Me: A problem indeed.

[@greendinosaurproductions3904]

Lol I'm like #69

[@katstevens2740]

I wanna like but

[@ayrpheli1299]

Mayterdome

[@jakepolls9843]

Maverick Scepurek underrated comment 😂

[@maverick-rs]

@@jakepolls9843 thank you/no ur comment

[@aqaisback9517]

I love when the intros are completely random due to the lack of context. “I have 23 BABIES.”

[@Creatorsan]

_Erasing babies_

[@flyingdoggo316]

_Makes more babies_

[@the_common_human2201]

_365 minus our 23 babies_

[@Avrauconiteros-Null_One]

@@flyingdoggo316 Lmao

[@FlyingPenguin196]

Wtf give them back

[@Uri_Ave]

My intrusive toughts are telling me to get 76 people that were born on diffrent days of the year and talk about this video being wrong

[@Culvers420]

i will support your intrusive thoughts

[@hv_2911]

my thoughts exactly :) but realised it would no longer be random as you "selected" people so followed a pattern

[@WhiskeyPapa42]

I remember doing this as an experiment in a math class with 26 people, and we had 2 sets of duplicate birthdays.

[@Grandflea02]

"I've got 23 babies" Gengis Khan: *That's cute.*

[@pointzerovr8516]

I had to look him up just to know how many kids he had

[@StolenTorchGuy]

@@pointzerovr8516 how many did he have ?

[@lesymon8483]

@@StolenTorchGuy _and he dissapeared, not sharing the number to anyone and leavong the question forever in the darkness..._

[@thatguykai9140]

@@StolenTorchGuy 14

[@speedwagon_69]

*he populated the amount he killed*

[@justin8287]

Man, imagine getting 100 people together to test this theory and then find out no one shares a birthday because you're so unlucky.

[@fridryx8464]

My whole grade when i was in school didnt share a bd the closest was like 1 day apart

[@RunningPieBOOM]

That's more rare so I guess its cooler

[@cullenpike6314]

Actually that would be extremely lucky bc only like .000001% chance that happens

[@snipergangdrob5940]

@@fridryx8464 My class of 25 has 8/25 kids share a birthday in the 4th grade ofc there was a pair of twins and triplets but 3 other people shared a birthday, (the triplets had a birthday on the same day as some other kid too)

[@hajilove7337]

420 likes. not liking but yeah gagaga

[@ScKTM68]

I had this problem in a statistic exam at computer science university, and yes... they asked us also if this paradox would have been useful for softwares and security was the answer. Very interesting topic

[@alexissliwak9716]

For anyone curious about the formula, it's a simple factorial where you remove lower numbers, keeping the higher numbers starting from 365 as you calculate the chance of NOT getting a matching date. For n = # of babies (23) And d = # of days (365) Chance of 2 with same date: = 1 - (d!/(d-n)!) / d^n Side note: factorial doesn't work how you would want it to when there is 1 more baby than the number of days(should multiply by 0, but the factorial of 0 equals 1)

[@-r-3656]

“I have 23 babies.” *Hold up.*

[@itsreeya3708]

the fact that this comment has exactly 23 likes... this is what i'm gonna cry about tonight.

[@user-ju2bk9ut8b]

It's true, i was the 23 babies

[@SaenzGoG]

223 likes, just saying, I love matches.

[@hugolink0655]

James Bonds constant "woman action" seems to have caught up to him

[@emegaly1526]

Wait a minute

[@banquo4223]

To be fair, they're all babies so I assume their birthdays are fairly close together

[@anissadunaway5415]

good point

[@leenmutwakil6350]

Smart 🤝

[@ashokmandal6982]

No, Even any adult has the same possibilities of the same birthdays as the babies , the possibility is still one of 365

[@MarkWatney]

In terms of birth year, Yes. In terms of birth date, No.

[@Neyobe]

Not really. A baby ranges from 0 days to 2 years old I’d say

[@halfcroisant]

I respect Kevin for drawing all of those lines just for 5 seconds in a video. Also I am born the 11th of March, pls reply. (i know I am late to the party and I know that Mark Rober is born the 11th of March as well)

[@Hussary2004]

One of the greatest videos in this great platform

[@blackskull7x]

Can't believe I'm watching this for entertainment

[@aftabhussain4036]

While having an exam tomorrow

[@127ante]

@@aftabhussain4036 you don’t have winter break?

[@konosxg7178]

Why not??

[@ComradeHeydi]

@@127ante yeah? I thought every one did

[@606movedtonewchannelsaeyou5]

@@ComradeHeydi Depends on the country, öy country doesnt have a winter break rn either. It’s ob the 22th January tho

[@aviksheetdasgupta1149]

Kevin : "I've got 23 babies" Me : Your wife, how is she ?

[@Allu681]

lmfao

[@KaosCurse]

To quote one of my new favorite shows: "Your wife must be so sore." - King Richard, Galavant

[@maisakalboneh2861]

wives*

[@silencekehew6895]

“To shreds, you say?”

[@aviksheetdasgupta1149]

@@KaosCurse 😂😂

[@lanewisdom6330]

Damn I always watch videos like this just to get half way and realize I’ve just been daydreaming about something else the whole time, now I have to rewatch it haha

[@Tooitoi]

Me and my cousin were traveling some years ago and we found a girl who shared same birthday and name as my cousin. What is funnier it that they both lived on the same state, traveled to another country and met at the same place while celebrating their birthdays.

[@BearPlane747]

W profile picture. RIP Fly high technoblade. Techno never dies!

[@griffincappin8567]

Nobody: People in math problems: I have 23 babies

[@jordanleethebeast5229]

Lol

[@cutiestcutcat514]

alexander Hawk And 49 cribs

[@andrepinho2328]

If Jhonatan bought 134 supercars, Alex train was 45 minutes late and light is faster than sound. How many water cups did Jake drink this week?

[@menacingthinker4322]

@@andrepinho2328 7.657

[@thevigilante401]

I liked and got it to 666

[@joshbray5036]

Worst Villians in 2018 ================= 2.) Thanos - Wiped out 50% of all living thing 1.) Kevin - Erased babies

[@thorjustus5794]

@Ялимон technically, yes. But it's still sad and mean

[@pokemonplace8903]

0. MF DOOM

[@porg3354]

Number 15: Burger King Foot Lettuce

[@mausam6101]

@@pokemonplace8903 0.5 MF Grimm

[@Calfea]

Josh Bray lol

[@b1oodzy]

For those that are interested, I ran a code 10000 times that ran the experiment with 23 babies and yes, it does come out to around 50%. But what I found more interesting is if we count multiple duplicates that it comes out to around 68%.

[@MrTrevortxeartxe]

Multiple duplicates out of how many people?

[@Beveyboygames]

There is a much better way for explaining this. Pretend you are in a room of 122 people excluding you, now you have a one in three chance of sharing a birthday with another person, because there are exactly as many people as one third the amount of days in a year, which is intuitive and makes sense. Now here's the trick EVERYONE has a one in three chance of sharing a birthday with someone else in this room because of the amount of people, now 99.99997% make more sense in a room of 100 people

[@nataliawrozek3867]

thank you, I literally struggled with understanding before reading that

[@Beveyboygames]

@@nataliawrozek3867 yeah it only feels paradoxical if you explain it really weird lol, he probably did it to keep the video going longer

[@rhinoj]

"If we replace our birthday babies with online passwords, . . ." ( 5:18 ) I didn't expect to hear that sentence today

[@B3XBP0]

Or ever-

[@kaylynnwalsh3311]

who did

[@Penta_I]

So did "VSauce! Kevin here. *I ' V E G O T T W E N T Y - T H R E E B A B I E S* "

[@badkarma6392]

In my basement 😏

[@Zielllo]

So when do you expect it

[@2acommunity]

As a teacher, I confirm this to be true. There is never a year where two students do not share the same birthday.

[@ts214121]

There were 9 birthday pair matches and a 3-way match in my high school class of about 100 students from over 2 decades ago. I wonder what the typical number is for a group of 100 random people.

[@obnoxious.]

That would mean that there is a 100 % chance, so Vsauce's math is wrong. I wish I was your student, I'd have straight As .

[@ganiz2944]

I’ve never had a year where two students did share their birthdays

[@user-ox5ir2rd6g]

@@ganiz2944 horseshit

[@theloneliestflowerinthefie1938]

In school I never shared a b. Day with anyone- mine is January 1st

[@generalludwig1637]

interesting how this also explains how real random shuffles don't "feel" as random with both video game maps and songs....

[@fruityskyline2237]

At the end, I wasn't expecting you to take a candle with the number 2. That is my birthday number and the month when the video was published is also my birthday. I think maybe you could try finding some math probabilities or paradox or whatever you want for those conditions to happen ! LOL !

[@satyakamshashwat]

Understood.. so basically, to make sure my password is secure, I should have at least 23 babies...

[@michalsadlowski1938]

Simples!

[@jasonclarkson3246]

Wouldn’t LESS babies be better? Because then there’s less probability of a collision occurring

[@phjorland]

@@jasonclarkson3246 So you mean I am 100% secure because I don't have children? :D

[@THEMATT222]

@@phjorland LOL

[@simonpichna4174]

this guy gets it

[@chloroclymor8388]

He says “343” right at 3:43 Coincidence? I THINK NOT

[@chloroclymor8388]

Idk

[@eman210rocks2]

This actually tripped me tf out but maybe that’s just cause it’s 6am

[@anshulgoyal597]

or is it???? *raises eyebrow in suspicion*

[@kevbri11]

good find my dude

[@Pablogotthesauce]

Also "365" at 4:05 which technically is 3:65

[@JarlHolta]

The probability is arguably higher than what you solved for, if we allow cases where we do not "stop at 2", we check further if two other babies have the same birthday in that group as well, and so on. Now if we sum it up we end up at 20 people is on average needed to generate a 50.5% chance of shared birthdays, due to multiples groups at times. There are other cases as well that can further increase such a number, say 3+ share the same birthday as well.

[@Disblee]

My aunt wanted all her kids to have the same birthday, 2 of them share a birthday, the other 2 are 2 days after the others

[@BlueJay567]

Weird that it seems everyone is getting recommended this right now

[@uwot9021]

ye

[@kayleigh8069]

merry christmas :)

[@gringerandom5872]

Yeah merry Christmas!

[@BlueJay567]

Thank y’all for the merry Christmas, merry Christmas to you :)

[@junimeme5626]

Probably some weird Christmas timing. Merry Christmas

[@ian8298]

_this guy:_ *me:* winning the lotto is 50% chance because you either win or lose

[@chrisguygamesyt9831]

Big brain move there

[@TheAbele992]

Lol I always thought as a kid that every single event had a 50% probability: either it happens or it doesn't.

[@emraldswrd]

@HanHanPlayz huh, do u know what chance means lol

[@miledacruz]

kinda

[@N3KLAZ]

@@TheAbele992 mathematically that's actually kinda true

[@patrickbrowdy5173]

I'm not sharing my birthday and location on a public forum, Kevin.

[@JMoney47]

Who here in 2024

[@SarahMaher-pl4lw]

Meh

[@besmart]

Kev, I have so much sympathy for you having to write on a dry erase board while left-handed. The struggle, it is real

[@quolack6435]

True, true

[@GeebleTheGarble]

You realise its the same the other way he just set it up wrong for himself

[@JakeLovesSteak]

I'm lefthanded, and I'm a teacher. I teach in a classroom with a chalkboard. I've stopped writing on the board as much as possible.

[@bardsonahill]

It's Okay To Be Smart what makes it harder then for right handed people?

[@premyaragarla3600]

Bards On A Hill We aren’t able to rest our hand on the board, at least comfortably. As you write, you start wiping everything away with you hand because you write left to right.

[@bunbunnylopunny1565]

From a graduating class of around 23 people, the oldest and the youngest shared the same birthday just a year apart. No one else in the class did, just them. Pretty cool.

[@emilyhellmueller]

my graduating class has the same situation, but i'm the youngest person! a lot more than 23 people but it's still pretty cool

[@thextremekittenmdj]

wait so how were they in the same grade?

[@emilyhellmueller]

@madapult my birthday is august 30 and so was the other girl's. the district allowed anyone to go into that grade as long as their birthday was before september first, but ultimately it's the parent's decision. so technically, she got held back but not really

[@MarpyPlarpy]

@@thextremekittenmdj It is extremely common for people to start school at both the age of 4 turning 5 and 5 turning 6.

[@InvagPrune]

@@emilyhellmueller same in the uk but with August 31

[@tolik_207]

in the whole school, I knew 70 people. and 3 of them had the same birthday

[@Speckled_Jim69]

Here's one for you. When I was 16, I was dating a girl that had the same birthday as me. Same day, month and year. We were both born in the same hospital in a town that had a population of 70,000. I left that town before I went to primary school. So I never meet her until I went back to that town when I was 16.

[@Alexd0t]

ok so this is crazy, I asked like 9 people and turns out we all had birthdays this year, how do you even explain that?

[@iamjohn2573]

Where did you ask tho

[@OhQueBacan]

@@iamjohn2573 lol, it went over your head

[@nicholasvalentino3291]

Dude this is a next level question

[@youngpyro9711]

Lmao well worded 😂

[@alexassassy5855]

@@OhQueBacan he just not misjudging people and taking for acquired the fact that people should be born within a temporal realm rather than chose their identity as a void intemporal protoss goat

[@anthonythompson928]

Wow. I did this as a fun experiment with some people in an online lobby. Turns out I had the same birthday as my twin brother

[@makcuja]

Wow so shocking 😱

[@sam_way2op491]

That's lit bro. Congratulations!!!

[@jgperes]

Woooow

[@stevawesome1424]

Lmao

[@ple8379]

OMG, nooooo! That's so sick, bro!

[@TranceSFX]

It helps greatly to view the day to month conversion table. I.e. day 238 of the year being in August for example.

[@redrob6026]

I once said this fact at a party, and then the first person I asked whose birthday it was had the same birthday as me. Everyone clapped as I walked away.

[@thebookworm1613]

Breaks a marker drawing the match lines for 23 babies. Proceeds to use new marker to draw match lines for 100 babies.

[@thecyryl]

lol

[@doszlopleonard6031]

For real

[@jasondeeprose3161]

correct

[@CapMan275]

No because notice no ink was coming out at the end, it was just smearing what was already there.

[@aamori3036]

Ian Lee that’s because that one probably broke too

[@aboboborinha4811]

Imagine him at the store trying to buy this many babies

[@yangsi3389]

🤣😂😂😂😂

[@cuboembaralhado8294]

they sell in packs of 100, I don't know why

[@fakefries5238]

@@cuboembaralhado8294 theres some funky mexican tradition where a baby that represents baby jesus is put in a cake and whoever finds him throws the baby jesus party next year. I'd assume bakers would use them freqeuntly when cooking the baby jesus cakes

[@cuboembaralhado8294]

@@fakefries5238 oh, ok, that makes sense

[@RSpracticalshooting]

@@fakefries5238 we had something similar at the catholic elementary school i went to. everybody got a piece of cake and whoever got the baby won a prize.

[@hafplace1346]

thank for explaining the wtf moment i had when i first realised in my class of around 30 i share a birthday with another person, and in my year group of around 180 i share my birthday with 3 people, including the person i first mentioned in my class.

[@chasechamberlain8721]

I would like to see 100 people come together and have a unique birthday and they are all one day away

[@girafpanda8886]

“BABIES! ERASING BABIES!” “Alright that’s not good” lmaoo

[@I_Cypher]

Erasing Babies is a cool band name

[@ihatesoup9242]

Ikr

[@wave._.hunter]

Fetus deletus

[@Flackzer]

@@wave._.hunter lmao

[@triciavanandler7285]

Hunter Schoonover I knew that joke would catch up to this eventually

[@Fayrayz]

It took me WAY too long to realize that the babies were actual mini baby dolls and not popcorn. This is what happens when it’s midnight and I’m hungry.

[@XDlosDominicans]

they can be popcorn if you want

[@Jen_TheSnail]

Both equally delicious

[@Fayrayz]

@@Jen_TheSnail 0_0

[@itzjagg5030]

@@Jen_TheSnail @fbi

[@MissLilyFae]

Big Kronos energy right here

[@MonkeShrubb]

Bro was drinking babies, it will be interesting to see how he will explain this to the police later

[@lepuluke]

I still can’t comprehend this. Why is it thou that we have hundreds of friends but no one shares the same birthday?

[@MonkeShrubb]

Incredibly, unimaginably unlucky

[@Milestone783]

teachers be like: “you didn’t show your work”

[@venum9663]

“That’s not the correct way of solving the question even though you got the right answer”

[@emsiyes]

"And because of that, I'm giving you an F"

[@speaar]

“And that’s why you lost your job”

[@Kenobisan02]

"The streets are calling my name"

[@raymiller5895]

@@venum9663 I only had one teacher that didn’t do that, she said, “I’ve never seen anyone do it that way before, you got the correct answer. Now let me tell you why that won’t always work. Oh, I’m not marking this as wrong

[@eben7248]

“Erasing babies...” *“...wait that’s not good”*

[@Hh-dz3ee]

I don’t wanna like cuz then it ruins the 69

[@icantswim3123]

Yes it actually is.

[@Amdocool]

My teacher erased my friends hand

[@lightbombs]

i also watched the video

[@davisharper6704]

Well, someone is finally against abortion.

[@maybemintmochi_]

I was so invested in this as a leap year baby T-T

[@-NeonZ]

This math was more complicated than my feelings

[@corbanspittka4436]

Imagine walking into a room with a single light and a man with a table with like a 100 tiny babies in a circle drawing lines....merry Christmas everybody

[@commenent8313]

200 likes and no comments? Hrm.

[@madisonchapman108]

315 likes and one comment? Hrm.

[@tazhingharib2573]

august 26?

[@nasti8506]

Hrm.

[@Enrique-Garcia]

"So, when were YOU born?" Oh no you don't, that's how I was hacked last time...

[@Steve-mg8tc]

69 likes on your comment

[@Steve-mg8tc]

Also I was born April 2 do you happen to be botn the same day

[@madisonchapman108]

@@Steve-mg8tc I was born on April 3rd lmao

[@Steve-mg8tc]

@@madisonchapman108 damn

[@hiimty4986]

I’m not relevant but mine is may 17

[@RyanDepauloDegenerateGambler]

It’s like hitting a 23 team parlay on 95+ % favorites so it actually makes sense

[@Mihail-Prihoda]

[@amalgamoon]

"I've got 23 babies"

[@violetforyou612]

Me Celebrating Birthday Random Strangers around the world: *Our Birthday*

[@user-df6vp1wo5b]

*COMMUNISM*

[@FirstnameLastname-uo3yu]

@@user-df6vp1wo5b Someone Called we?

[@kennethmalloy3437]

This is Mother Russia in a nutshell

[@josephstalin364]

Me: Has a birthday cake My siblings: OUR CAKE

[@GizmoHey]

A friend of mine shares the same birthday as me. So Yes it's OUR BIRTHDAY

[@liz-ck9pz]

man's lost me when he sneaked a ! into the equation

[@daniaalh1864]

haha the ! means ‘factorial’ - essentially the number multiplied by every number before it. for example 5! is 5x4x3x2x1

[@Retrenorium]

@@daniaalh1864 isn't that the same thing but harder than to simply multiply the current number by the previous result? 2x1=2 3!=6 2x3=6 4!=24 4x6=24 5!= 120 5x24 = 120 6! 720 120 × 6 = 600 + 120 = 720 Etc?

[@unlqvt]

@@Retrenorium well yes, thats basically how calculating the factorial recursively works, meaning that you need the previous result in order to be able to calculate the next result.

[@daniaalh1864]

@@Retrenorium if you’re in the lower numbers then sure but it’s the same thing really. when you get to large numbers like in the question, like 365!, it would be inefficient to sit there doing the work manually when you can use the ! function to get the answer immediately - for reference 10! gives you 3,628,800, so 365! would be an impossibly large number to work with. It also means you don’t have to write 365x364x363… endlessly to get to 1.

[@rodisfishing1647]

this is so fascinating, in 5th grade to up until now (11th) we had from 25-28 students and 2 of those share the same birthday

[@richardfowell490]

Think that’s the first time I’ve seen factorial (!) being used since university. I’m proud my education has finally come on useful😂

[@BAC0NWOW]

stares into camera... "ive got 23 babies" this is why I love vsauce

[@laloreyes7017]

me: what’s the wifi password friend: it’s on the back of the router the back of the router: 6:17

[@nathanharding5259]

Pineapple Underrated comment

[@tan5184]

lmaooo

[@valscripted]

Pineapple this is so accurate 😂

[@Dizee.]

7:22*

[@johnmendeja1777]

Bruh the password is 12345?? Dat wrong

[@EarlJohn61]

He should have qualified his statements with something like: "With 23 babies there is a 50% chance that there will be *at least* one pair with the same birth date."

[@zoe127]

KZbin really showed me this on my recommendations on my birthday

[@lordjehovah3598]

Vsauce at the shop: Please may I have 75 fake plastic babies please Cashier: WTF

[@geminin6674]

Were they bought from a rubber man?

[@daemichelle]

I thought there was 100?

[@jadenramadhar4340]

He prob thought of that and ordered it

[@itsbunnz5295]

Btw I just wanna day these baby’s are from a king cake, which is a thing in the south and you find baby’s in it, it’s really weird look it up.

[@awesomemantroll1088]

He's the guy we read about in math problems

[@dominiksipos7836]

I'm not really sure that I understand this, but..... Merry Christmas! After one year... I still don't understand. Merry Christmas!

[@vlad_k0o291]

Happy babys or birthday or holydays...u get the point

[@maddiem1908]

Merry Christmas to you too, Dominik!

[@TailorJulz]

Marry christmas me too

[@tianna_is_online]

merry chrisler

[@nc7880]

Merry christmas :)

[@barbaquebells2574]

My old English class assigned seating by birthday. I got close to a kid named Antonio and he had my birthday. On e day we were geeking on that when we realized. The girl next to us, Laura said “That’s my birthday”

[@DME3-ms4yz]

Just imagine in a classroom, theres a high probability that your classmates have same birthday and I prove that

[@minkmiau]

Someone from my 17 people class shares my birthday

[@kaiserxyozni4786]

Can we just admire that Kevin literarily purchased 100 baby dolls

[@dimi7621]

And also that he gave the effort to put them all one-by-one in place

[@jadesketch1726]

Do you know where he bought those ?(i want little baby dolls)

[@nattidahelsinghof2306]

Jadesketch no but i wan one

[@payton4786]

you can get them off amazon, all the juniors at my school has littered the school with them

[@purgatorian1616]

@@payton4786 must've been inspired by Jordan Cunninghams hiding mini babies video

[@greta8555]

can’t believe I clicked on this video thinking it was called the britney paradox

[@antoniovergotti1895]

Same_

[@javieraossandon2713]

LMFAOOO I can imagine you being like "why the hell is he putting babies in the table"

[@rbyln3112]

I thought it said “happy birthday paradox” ;-;

[@Helianthus_]

Oh baby baby, how was he supposed to know that something wasn't right here?

[@dr.downvote]

Can't blame after seeing the name Greta! Jk, no offense to you, all goes to Greta thunberg lol

[@darkzim3872]

I had always known this but in a different kinda way when I was small and I attended a primary school the school only had about 50 pupils in morning we would have a assembly and if it was your birthday you could choose to play a record with your favorite song on the amount of times we would have to listen to two sometimes three and a few times 4 songs in the morning I'm guessing the odds where bigger because people who's birthdays where on a weekend or holidays would play them on the Friday before I remember the head teacher after one morning telling us that Gershon Kingsley - Popcorn was no longer available as the previous week it must have been played at least 10 times and 3 times in one assembly, I guess the kids just loved that song

[@dariocaporuscio8701]

That explains why I have so many close people matching their birthday with other people I know, I thought it was a coincidence but it's actually a predictable situation

[@tibees]

When you discover plastic baby shower accessories on eBay

[@texxylady]

I saw those at the dollar store about six months ago and the geek in me got uberexcited

[@RazorM97]

lol, u kiddin

[@themothman4935]

They are also on wish

[@abranbsingh1024]

hey...long time Ms hendy... i hope that cat's okay!

[@dylanwoodside3102]

Imagine Kevin going to the store and just buying like 100 tiny babies

[@pavlemilosevic8224]

That's why he order it using vpn and using address of abandoned house 🤣

[@cheekibreeki904]

Sounds just like something he'd do.

[@tonyhakston536]

Imagine this comment without context.

[@heavenwafflesdestroykidwho6142]

100 likes 👁️👄👁️

[@CYB3Redux]

@slam zamillion r/WHATTHEFU-

[@aymanazad1443]

legend said he drank all the other babies

[@jetplanewastaken]

0:06 i love the way he just says that nonchalantly

[@nicholaswensink2314]

A lot of people are misunderstanding this, saying something along the line of “but there are 100 people in my ______ and I share a birthday with none of them”. The probability here is saying there’s a 99.7% chance that at least two in the sample will share a birthday not that you specifically will.

[@mulymule12]

Yeh, make's perfect sense with an ounce of thought. 99.7% chance that 2 will share a birthday in a sample of 100, but that still leaves a 1/50 chance that will be you. Or 2%

[@azlan194]

Yeah, a lot of people are confused about it. Another way to put it is like, the probability of SOMEONE winning a lottery this month is very high (almost every month there's someone winning lottery) but the chance of you winning it is almost 0%!

[@MrHasas963]

The first comment i get. But why did two ppl just confirm what does not need confirming? You you think the guys is right, theres the like button.

[@MrHasas963]

@@mulymule12 the way i think you should look at it tho is that there is a 50 %chance from your perspective. You will either find one or not. I wouldnt bother because i dont rly want to meet a 100 babies

[@atriyakoller136]

I am a teacher who teaches small groups of students. I have a birthday on December 31st. And in October I had two groups where I had a student with a birthday on the same day. It was cool.

[@tigerwoods4034]

I went to high school with about 800 guys and everyday during announcements they would shout of the birthdays. It was not uncommon that nobody had a birthday that day. I didn’t know how statistically crazy this was.

[@nathanbensoni469]

Hmmmm

[@stijnkemper7103]

I rlly need to think to understand this sentence, u could'va said: It was common that nobody had a birthday tbat day😂😂😂

[@PurpleMoon799]

probably in august 😉

[@MaryJane-tp3qd]

My freshman year had 1,800 kids and now I wish they told us people birthdays :(

[@HannaSis]

My school does the same thing and I don’t think that anyone shares the same birthday except for these 3 girls in my class who were all born on the same day, during the same hour 😂

[@devaansh_verma]

Fun fact: my brother and I almost shared the same birthday. Mine is on the 14th and his is on the 15th. My mother said it was my birthday so she wanted to have the Caesarian the next day. Thank god.

[@NxnjaSenpai]

Speaking from personal experience. I went to a small high school where each elective class was made up from the same pool of about 50 kids all born within a 6 year range. Not only did the yearbook show that two of my friends shared the same birth day but they both shared the same birth date. They were not related.

[@wateenabutaha4871]

I did not understand a word besides babies and birthday 👍🏻

[@evangelinegamali3374]

Seseme seed

[@husseinazher]

Me2

[@applepie1272]

oh Babies and Birthday's are TIGHT

[@lucytenden7975]

that’s bc he was trying to make it sound cool and confusing by calling them babies when he rlly means any human not just babies. But if u think about it, obviously there’s a big chance 2 out of 100 people would have the same birthday out of 365 days just not born on the same year.

[@hicrhodushicsalta4382]

@@lucytenden7975 that's cause it's simple probability (n/k) everyone does this in 9th Grade or so...

[@konica_7396]

I've watched this three times, all in different years and different times, and everytime I am more surprised. Not only by the video itself but also my tendency to forget things

[@stonerbland7621]

Damn I was just feeling this

[@mars2_u782]

life takes us on a mysterious road and forgetfulness tend to happen to us as many information are being absorbed into our mind

[@hxhdfjifzirstc894]

An easier way to think about the question is to imagine 365 babies. Would it be at all likely that each one would have their own unique birthday? Hell no, that would be some kind of freak accident.

[@sinfulblacksoul]

honestly same 😭

[@Red80008]

:D

[@LotusMouse]

Bro was hiding his tears when he erased the 100 baby web thingy

[@curritomb20]

Hi there! Great video! I think you are missing an 'at least' every time you express that 'two of them share a birthday'. Great job anyway!

[@hannahturner6629]

it took me so long to realize the “babies” weren’t popcorn

[@katongules2346]

I thought they where teeth

[@MetrioGaming_]

I thought they were dogs

[@EXA1024_]

@@MetrioGaming_ wΗαt

[@cjfdnqkn4374]

I thought they were drops of coffee

[@zooeysmith529]

How did you know what i was thinking?

[@BrooklynBwoii]

As long as 70 people are watching this video at the same time, there is a 99.9% chance that they will have the same death day but in different years.

[@lunabirdzzz6604]

Dang. That's my only response I can find in my head.

[@chisinau1302]

Now he's more popular, so more people watch the video at the same time.

[@puginator1612]

*WHAT*

[@SkylarGlider]

deep

[@simbg5146]

No?

[@rufuspipemos]

This explains why, as a kid, I would get many baseball cards of the same player after buying just a few packs, even though there were1,400 players in the MLB.

[@FlorizDev]

How many people do we need for 3 people to share birthday at 50% chance

[@unboiledegg5765]

2:50 “Babies.......... erasing babies....... Ok that’s not good” -Kevin 2018

[@MaxTheCat-eh5ts]

Unboiled Egg oof

[@mechacode8527]

Wow... I have read comments that claim to see a comment quoting the guy in the video in the exact time the guy in the video says it... I thought it was very hard for that to happen, but that has just happened to me with your comment.

[@KitsuneCentral]

Mr. VSauce, I don't feel so good.

[@gqh007]

Fetus deletus

[@GarfieldPhone]

Abortion

[@JVR10893]

“You have the same chance of being born on one of the 365 days in the year”. Press F for leap day babies.

[@hannahharrow8425]

I'm leap day kid 1996

[@fluj5170]

im the party pooper that ruined the 69 like count get rekt

[@familyali795]

@@hannahharrow8425 lets go twin

[@eyesonfiresettopanicatthew276]

@@hannahharrow8425 so.. Ur six now at the end of the month? grats!!!!

[@NPW007]

If you are born on the 29th of Feb than you get to choose the date of your birthday is on the 28th of Feb or the 1st of March

[@ASd-mg5gs]

I really love michael's video, even though i don''t understand almost nothing!

[@brodakarat6340]

i swear every time ive come across a probability problem that has me stumped, i just negate the thing i want to find out and it becomes trivial

[@CarlaSofieFM]

Him: *pours tiny babies onto table* "Ive got 23 babies" Me: "Cool"

[@eziesan6362]

Drengerøv

[@hencodelange9289]

He's the guy from the math problems

[@pengii6804]

Bruh subscribe

[@obviousb8508]

Oh damn fr?

[@sprsn1279]

There used to be 24

[@mattson4552]

kevin- "I've got 23 babies" *FBI OPEN UP*

[@jarenfoster9409]

XD

[@JackyDacky]

*-FBI OPEN UP-*

[@peneloperose1856]

Mattson Claybrook hahahahhah

[@jacktierney3245]

one mother, or...

[@caritahearts2405]

Kevin: *takes sip of mug* *23 babies fall out of mug* Me: delicious

[@lucasho-hz4tt]

I’m still wondering why he has 75 model babies

[@richardadkin5340]

i have way more i just see how many i can throw into a cup