Circles: radius, diameter, circumference and Pi | Geometry | Khan Academy

[@canuseetheuglybirdie6599]

just want to know how he can write perfectly on desktop

[@AngelFire-gh8dw]

Hes probably been doing it for awhile

[@floridmonkey2723]

I thought he used a Wacom tablet too.

[@danellet1365]

He uses some sort of drawing drawing tablet.

[@blakezabala3846]

He uses a not pad and uses a special pen. I thought how he wrote awesome too...he is using almost like a Promethean board.

[@animationspace8550]

Like dis? π< a perfict piez

[@thesaaturn]

Me and the bois whatching khan academy in quarantine

[@shrekster5713]

me and the boys watching khan academy during the second quarantine ;(

[@BilalAli-rh2cx]

Shrekster5 lol

[@stephenbrown1878]

hey does anyone does zooms for this type of math?

[@christophergonzalez8883]

@@shrekster5713 lol same here man

[@Ethan-pu5lo]

Noice

[@michaelmag1095]

Another excellent explanation from khan academy. Explaining how the formula was originally established makes it so much easier to comprehend.

[@rosydevils3390]

I completely agree! (yes ik this was made 6 years ago)

[@Sansatu23]

you are literally the greatest person alive. You saved me from a F in my math class

[@Lily-mm8ew]

Because of online school I went from an 100 in math to a 0 looll and sadly these aren’t helping rip

[@alaadarwiche4352]

Lily lol I can already see! They don’t say “an 100” they say “a 100”! I use to take 💯 to! But now, I am at 95😔😔. But I am trying my best!

[@huyuht]

help me

[@Lily-mm8ew]

tarek nigeria bruv what? I ain’t ever heard anyone say “a a hundred”

[@nikkiblack6546]

@@Lily-mm8ew right

[@rainstorm.]

Omg bless u I have a circle geometry test tomorrow

[@kakashihatake1376]

Blue Pearl same here

[@zeleakatjingisiua4234]

I'm obviously writing Friday or next week Monday imagine that

[@afrazmustofa3814]

same

[@sheliadavis4901]

I have to do a scale model of Pluto😰👿😢

[@RandomPerson-sh5uv]

Blue Pearl same

[@crbaade]

As a mom trying to homeschool in 2021, this is so valuable. I love how he explains it step by step.

[@nathanielackman1019]

i think i did a funny, teacher: king arthur invented the circle table. Student: no it was sir cumference.

[@Mars_-mi4di]

Nathaniel Ackman lol

[@channingnicholson4275]

Mel c lol to you too dude hahahahhahaha

[@maheenFahad]

U talkin about pac-man

[@wrec6367]

Dinkleburg

[@ashleyrojas6419]

im too dumb and i have a test tommrow that determines. my future

[@Raddrizz]

How'd it go?

[@florpbosh3079]

Yeah how did it go

[@nia.r5988]

How'd it go?! We wanna knowww

[@florpbosh3079]

@@nia.r5988 he probly not gonna anwser 😂😂why it sound like a sentence when i said ur name wit my text

[@prastuti4264]

How did ur test go Ashley?? Probably you got an F

[@christylabarbera2921]

I'm a 55 year old college student who has always been horrible at math just trying to pass the Praxis. This is the best explanation of Pi ever!! After all these years, I understand. Thank you!!

[@penginator89]

wait what 💀 how are you 55 and still in college?

[@christycreates1731]

@@penginator89 Easy, I went to college late in life. Not everyone goes right after high school.

[@wowomgcreative]

thats like retireing age how did you just get to college

[@christycreates1731]

@@wowomgcreative I hope that's not a serious question. If you can't figure it out, maybe you need to go to college.

[@manuel5114]

@@wowomgcreative Here in Argentina most Universities are tuition free and open to everyone who graduted from high school, so there are many elderly people attending University. Of course there's no age restriction in paid Universities, but having to pay a tuition may be a deterrant.

[@sophiarodriguez1861]

Khan is probably the BEST teacher ever!! thanks!

[@luxfries1524]

Organic chemistry is second best

[@arunjohny]

@@luxfries1524 Who is the best in organic chemistry?

[@amigo7672]

khan’s probably the teacher we’ve always wished for but never got

[@kenyan3057]

Omg. I've been doing this for the last 5 yrs of my life and never understood and understood it by half way through th video

[@alaadarwiche4352]

I didn’t

[@stephenbrown1878]

Have you started understanding this math yet? I need help.

[@pariswilliams2986]

thank you so much, you are the best teacher ever! with that 11 Minute video, you taught me more than I would have learnt in 2 lessons!

[@brandonseto4524]

I actually understood this in 10 minutes besides my math teacher

[@derickhernandez7123]

5:28 “they gave it a nut”

[@selenawright1332]

and this why we failing geometry 😂😂

[@ryanchong4372]

Thought no one noticed

[@Oofmart]

lmao

[@shruti4s745]

reasons why Im failing math😂

[@robloxrox9502]

🤣

[@pham6238]

Diameter is a line goes straight through the center of a circle Radius is a line goes to half of a circle Circumference is the distance around the circle If you want to find circumference, get the diameter multiply by pi EDIT: OMG GOT SO MICH LIKE THANK YOU

[@lydiasimpson586]

OMG THANK YOU SO MUCH I FINALLY FIGURED OUT A PROBLEM IVE BEEN STUCK ON FOR 40 MIN

[@razanabanana587]

listen to the circle song

[@brotherlance]

PopBAT thanks

[@isavenewspapers8890]

(To start, when I say "circle," I'm not counting the inside region as part of the circle. Technically, mathematicians call that region a disk. Don't go correcting strangers about that, though.) It's better to think of a radius as a line segment going from the center of a circle to a point on the circle. You can draw any such line segment, any radius of the circle, and all of these will have the exact same length, no matter which way you go from the center. This length is sometimes also called the "radius" of the circle. This fact is what makes circles a special shape. In a way, the radius is the property that defines a circle. Because of this, a radius is much more than just "half a diameter."

[@hausofamelia]

Wow, this made it seem much more simpler than it seemed to be! I finally understand, so thank you. :)

[@ambercaesar4560]

The public school system has failed me greatly. It took me 24 years to fully understand something he explained perfectly in 11 minutes. Thank you Khan Academy!!

[@randomlotus8806]

Man, thanks. This helped, I don't know. My math teacher never explains right. No one in my class understands him. They all just learn the material on their own.

[@thericefarmer2271]

Play at 0.5 speed if you want to hear a drunk man and start rolling on the floor laughing.

[@DebbyWhitehead63]

+DanTheCakeMan Haha

[@actuallyel8936]

+DanTheCakeMan I am so doing this.

[@actuallyel8936]

+DanTheCakeMan To get creepy-crazy-fast math geek play at 2 or 1.25 or 1.5 xD

[@thericefarmer2271]

IcePlayzRolePlay AphmauFanFic xD Yeah I tried every speed. Lol. Love the new speed changer

[@uravrgmemer8177]

U bloody legend

[@mariagarceteabea2748]

Who's scrolling down the comments while watching this 😂

[@priyasakhare9764]

Me 😒

[@subhaarul8025]

Meeeeeee

[@jenniferrivera6922]

me im soo bored

[@oliverwilliams4347]

me:p

[@risesthestars]

Maria Garcete Abea meee lol

[@oscarb1582]

Though I was able to follow this very easily I can understand why others can't

[@fantastic_fox0918]

Wdym if you’re saying this the way I think it’s just everyone learns at a different paste and there’s always something someone’s good at and then isn’t good at.

[@meyouweaboo1551]

@@fantastic_fox0918 did you read it?

[@fantastic_fox0918]

Me You Weaboo ohhhh sorry I thought you said can’t lol 😂 I was a little tired that day

[@kawaiipandajoy8101]

it really helped me catch up when I'm absent at school coz I'm always ill

[@idontknoe6454]

Kawaii PandaJoy same

[@splatty6863]

Can I get the snap

[@Brandon-sy2du]

Mmmmmmhmmm.... sureeee

[@alaadarwiche4352]

Same as my sister omg my sister has a twin lol 😂

[@whotheheckis_ray]

My teacher has been recently absent and we've had many substitute teachers come in which interrupted me and my classmates curriculum for math, when we got the lesson on Circles I had no idea what I was being assigned and thank you so much for this video teaching me more then school.

[@imanmarrianamontgomery6992]

Now I understand the area and circumfrance of a circle. YAY!!

[@imanmarrianamontgomery6992]

cool

[@Taybansss]

hey what grade u in

[@stephenbrown1878]

Wow i'm glad you understand I need a little help?

[@Poli1348]

Great last minute studying before an exam. All said.

[@thanos6818]

This helped a lot but how does he write so good on desktop? I CANT EVEN WRITE GOOD ON PAPER, please help xd

[@sumanshekhawat3209]

Suck Thanos we like avengers

[@alchemy-the-animated-series]

Thanos I think he used a stylus

[@chloemacdonald9325]

@@alchemy-the-animated-series Wacom Tablet

[@lomaatmeh2854]

Thanos is trash and thor is the strongest avenger

[@Imgbycin]

Loma Atmeh no one cares

[@tubeisace]

I wish they'd taught me like that in school! So easy to understand now! Thank you!

[@swisszz]

This comment is so old and this video too lol

[@azucena-hm2wo]

how are you doing now?

[@gfdgf2]

you have just made clear to me what my math teacher had failed to specify for 12 years of school. may god rain his blessings upon you. p.s r u related to ginghis by any chance? thanks

[@alvindueck8227]

Ok. How would you get the circumference of an oval

[@talevaters0720]

still the same bro

[@abdalrahmanamrmostafa1975]

@@talevaters0720 no

[@nightcorenymph358]

You saved my grade. Why can't teachers talk like this? It gets their point across.

[@wartortle577]

Confused..What if the question asks something like "Suppose the circumference of a circle is 7π. What is its diameter?" They don't use the meter unit

[@jamaabdulle3050]

cos ur dumb

[@legendary436]

14 pie aka 14x3.14

[@minhaj283]

wartortle557 to work out any sort of question like this u need to know the basics of rearranging formulas. If u know 7π is the circumference then basically it is πxd=7π therefore diameter=7π/π which is of course 7. So 7 is the diameter. If there is no unit then just leave it as a bare number but almost all the time there is always a unit.

[@RachelKimJaceMordecai]

jama abdulle No need to be rude.

[@Ronie12]

jama abdulle Based by your typing and his typing....Your the dumb one XD

[@andyh8700]

Awesome you made me understand so much better about the Circle, keep up the great work!

[@metronini]

Thanks Sal for the help

[@abelmontoya3180]

"Some order to it all." God is good.

[@masteroids]

This is really helpful for my daughter in math class!!

[@Minnielovelove]

thks so much i have to prepare for a maths test tomorrow and u helped me!

[@MrMoeqt]

An irrational constant which is the ratio between the circumference and the diameter. It has no end, and no repeats. It begins something like 3.1415... etc, it has an infinite amount of decimal places. We can only approximate pi to a certain number of decimals places, but a handy approximation of pi is 22/7. But another interesting fact about the number pi is that it can never be expressed perfectly as the ratio of two integers. We are able to make approximations like 22/7 but we can't be exact.

[@alifhossain9463]

he is so smart this is helping me a lot he even does in my lauguage

[@EspressoLegalPh]

please make some videos about geometry.. thanks for this vid btw very very useful for our exam tomorrow ::D

[@tiaankreeft8156]

11 year old comment

[@GrantDavis]

Almost to the point of acing my SAT practice tests, took geometry in 8th grade, this serves as just enough review for me to be proficient in it again.

[@sssssunyy]

i love u guys sm . im in special education because i didnt go to 5th or 6th grade and im really behind . im still not on track yet but i’ve been reviewing lots of the important stuff from those 2 grades i missed . khan academy might actually save my future

[@DJBailey99]

Thank you so much you saved me my week of lunch times and deducted a week of after school detentions! THANK YOUUUUUUUUUUU :)

[@greenforests6239]

thank you so much

[@priyasakhare9764]

Thnx I HV a test tomorrow and I'm all prepared

[@alchemy-the-animated-series]

Priya Sakhare I thought u said you have HIV

[@Z3R0C0NTENT]

Khan Academy is so useful and easy to understand!

[@GetJammed_]

This insanley helped me understand the things taht my teacher said to wait until it is time to learn it. Thanks so much Khan Academy!!!

[@bitter-to-better]

Khan academy is probably the only videos I understand. Thanks so much I have a math exam tomorrow. This might seem dumb, but why do the call the length going around the circle circumference and not perimeter??

[@adiliamaxwell2992]

He is a good person he is not one of those people who wants subs he just wants to help. So keep up the good work.

[@talevaters0720]

thanks man! i have an exam tomorrow :D LIKED!

[@wy19440]

Good

[@kenciolek843]

" O " occurs in the King James Bible over a thousand times

[@asgharibegum465]

u are the best u saved my life thnx

[@GamerRocket]

Well, in search for a video to help me out with Pi, this video did just that, in fact it went over expectations. Impressive :D

[@kaitlyndai4290]

TANK U! this helped a lot :)

[@jamaabdulle3050]

its ok cutie

[@rahimabegum8739]

+jama abdulle creep...

[@vishrutkinikar2311]

Awesome video, Using this to prep for school Thank you!!!!!!!

[@lunadreamystrz7875]

Currently watching this to help study for an upcoming test in my advanced math class, which I'm currently on the road to fail, but I hope this will help, I'll update if it does! :)

[@timothygough789]

A go-to for instructional practices at any students pace.

[@realyashshukla]

Thanks for giving your knowledge to us ❣️

[@Panther-ln9xy]

Sup guys say the first 100 digit of PI (3.14159..............................................................)

[@amandacatalano461]

im in 7th grade and im struggling but this helps so much so thank you

[@shameemafarhana5201]

What curriculum is this?

[@0wolfplayer0]

0 : A circular shape O : An oval D : A semicircle . : a... Point? 8 : 2 circles The world is so full of circles!

[@ProAmpharos]

pi r squared = area of the circle so lets say that a circle has a radius of 5cm, then we do: 3.14 * 5 squared. keep in mind, do Radius Squared before. It's the order of operations.

[@MathDotCom]

It makes my concepts more clear for teaching my students

[@aryanakularathne9467]

Wow, this made it seem much more simpler than it seem to be! I finally understand, thank you very much Sal!

[@Rizzyminecraft]

13 years later .... U still helping us

[@meyouweaboo1551]

Can't wait to use this information after I graduate

[@giraffequeen4110]

right? 😭

[@Thefoohimus]

Thx for this vid it always helps me learn.

[@ngarcia1995]

I love these video's! If my math tea her actually did her job instead of flirting with the boys ha

[@alltimelowinzasion]

thats not how pi was calculated. it was by expanding what we know about regular polygons to a figure with the number of sides approaching infinity, which is, for all intents and purposes, a circle

[@blakezabala3846]

So there is pi, we just cant eat it :(

[@realseniourtaco5283]

Zabala lol

[@blakezabala3846]

xD

[@priyasakhare9764]

XD

[@spooktspeek]

if you write it on paper and then eat it you can eat pi.. but it isnt tasty.

[@TheSkaterdude789]

it is related cuz u have to multiply the diameter by 3.14 (which is PI) to get the circumference

[@necker-zs7yu]

Bro, I came back from school without understanding a thing that my teacher said I completely understand the subject and THANK YOU

[@johndavetitular9924]

OMG THANK YOU SO MUCH... IT HELPS ME A LOT... GOD BLESS YOU!!! MAY YOUR CHANNEL GROW UP... IT DESERVES TO HAVE MANY MANY SUBSCRIBERS SPECIALLY STUDENTS AND TEACHERS...

[@adeelansari578]

Very good

[@LamePrincesss]

THANK YOU KIND SIR ❤️❤️

[@Toast_Charms-lm6mr]

thank u

[@viennatung9145]

Thank you Khan Academy

[@irkiIIer]

for the first time in my life i finally understand wtf pi is

[@brandonbrinker6592]

thx this helped alot

[@alyssarodriguez9639]

OMG.... This is helped me soooo much with mi homework!!!!! :)

[@Tonyrosama]

There is a coastline near (lets say near L.A.) that is measured and someone says "this piece of coastline is 16 miles long." then another guy goes out and measures with a finer ruler, he says "no!, the coastline is 16.13 miles long!" and so on forever. The real answer is that the coastline becomes infinitely curved and twisted as you shrink the ruler smaller, just like a fractal. A circle is like the coastline, you can not find a smallest angle to measure a final number in the ratio!

[@Bonnie-nn4zo]

Pi=3.141592654

[@Bonnie-nn4zo]

Lol

[@callummine]

pi = 1/1 +1/3 +1\5 +1/7 ...........

[@radicalrica]

pi= diabeetus

[@spsindia2001]

wow this made me much more simpler than it seem thanku so much

[@sidahmedbilalbilal6415]

this is legit the most helpful thing in the world, now i am not going to fail class

[@kekships]

pi = 3.14159265

[@floridmonkey2723]

You forgot a few numbers let me continue. 35897932384626433832795028841971693993751058209749445923078164062862089986280348253421170679821480865132823066470938446095505822317253594081284811174502841027019385211055596446229489549303819644288109756659334461284756482337867831652712019091456485669234603486104543266482133936072602491412737245870066063155881748815209209628292540917153643678925903600113305305488204665213841469519415116094330572703657595919530921861173819326117931051185480744623799627495673518857527248912279381830119491298336733624406566430860213949463952247371907021798609437027705392171762931767523846748184676694051320005681271452635608277857713427577896091736371787214684409012249534301465495853710507922796892589235420199561121290219608640344181598136297747713099605187072113499999983729780499510597317328160963185950244594553469083026425223082533446850352619311881710100031378387528865875332083814206171776691473035982534904287554687311595628638823537875937519577818577805321712268066130019278766111959092164201989380952572010654858632788659361533818279682303019520353018529689957736225994138912497217752834791315155748572424541506959508295331168617278558890750983817546374649393192550604009277016711390098488240128583616035637076601047101819429555961989467678374494482553797747268471040475346462080466842590694912933136770289891521047521620569660240580381501935112533824300355876402474964732639141992726042699227967823547816360093417216412199245863150302861829745557067498385054945885869269956909272107975093029553211653449872027559602364806654991198818347977535663698074265425278625518184175746728909777727938000816470600161452491921732172147723501414419735685481613611573525521334757418494684385233239073941433345477624168625189835694855620992192221842725502542568876717904946016534668049886272327917860857843838279679766814541009538837863609506800642251252051173929848960841284886269456042419652850222106611863067442786220391949450471237137869609563643719172874677646575739624138908658326459958133904780275900994657640789512694683983525957098258226205224894077267194782684826014769909026401363944374553050682034962524517493996514314298091906592509372216964615157098583874105978859597729754989301617539284681382686838689427741559918559252459539594310499725246808459872736446958486538367362226260991246080512438843904512441365497627807977156914359977001296160894416948685558484063534220722258284886481584560285060168427394522674676788952521385225499546667278239864565961163548862305774564980355936345681743241125150760694794510965960940252288797108931456691368672287489405601015033086179286809208747609178249385890097149096759852613655497818931297848216829989487226588048575640142704775551323796414515237462343645428584447952658678210511413547357395231134271661021359695362314429524849371871101457654035902799344037420073105785390621983874478084784896833214457138687519435064302184531910484810053706146806749192781911979399520614196634287544406437451237181921799983910159195618146751426912397489409071864942319615679452080951465502252316038819301420937621378559566389377870830390697920773467221825625996615014215030680384477345492026054146659252014974428507325186660021324340881907104863317346496514539057962685610055081066587969981635747363840525714591028970641401109712062804390397595156771577004203378699360072305587631763594218731251471205329281918261861258673215791984148488291644706095752706957220917567116722910981690915280173506712748583222871835209353965725121083579151369882091444210067510334671103141267111369908658516398315019701651511685171437657618351556508849099898599823873455283316355076479185358932261854896321329330898570642046752590709154814165498594616371802709819943099244889575712828905923233260972997120844335732654893823911932597463667305836041428138830320382490375898524374417029132765618093773444030707469211201913020330380197621101100449293215160842444859637669838952286847831235526582131449576857262433441893039686426243410773226978028073189154411010446823252716201052652272111660396665573092547110557853763466820653109896526918620564769312570586356620185581007293606598764861179104533488503461136576867532494416680396265797877185560845529654126654085306143444318586769751456614068007002378776591344017127494704205622305389945613140711270004078547332699390814546646458807972708266830634328587856983052358089330657574067954571637752542021149557615814002501262285941302164715509792592309907965473761255176567513575178296664547791745011299614890304639947132962107340437518957359614589019389713111790429782856475032031986915140287080859904801094121472213179476477726224142548545403321571853061422881375850430633217518297986622371721591607716692547487389866549494501146540628433663937900397692656721463853067360965712091807638327166416274888800786925602902284721040317211860820419000422966171196377921337575114959501566049631862947265473642523081770367515906735023507283540567040386743513622224771589150495309844489333096340878076932599397805419341447377441842631298608099888687413260472156951623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[@bannaduckwht2515]

@@floridmonkey2723 lololol

[@munemmatin1284]

thanks man i passed this part on my test!

[@user-rg8oe]

my exams tomorrow and I just noticed I don't know anything about this stuff! thanks!

[@prestonlarayapp8043]

What are you finding when you find the square root of the circumference of a circle?

[@flameripple]

Thank you SOOOO much you SAVED my math homework!

[@danielwylie12]

Please sir, I have been struggling to determine the answer to the following question for months. I know that if an object travels along 25% of a circle's circumference that it will traverse 50% of the length of the diameter in terms of three dimensional space and I also know that if an object travels 50% of a circle's circumference that it will traverse 100% of the diameter. This would make it seem as if there is a linear relationship between the two but is this true? If an object travels along 10% of a circle's circumference will it traverse 20% of the diameter?

[@bluesweatshirt8466]

THANK YOUUU i was so confused :D

[@tommaassss]

this is the best channel on youtube

[@gigihanscom4307]

YOUR A LIFE SAVER!!!!

[@YourHorrorWh0re]

Thanx you helped alot

[@px_chy6716]

Tysm now I’m not worried about my math essay anymore :D

[@ryanziegler4403]

this helped me so much

[@rebeccaw113]

Very helpful!!! Thanks!!

[@mylotraxlegacy5328]

This is amazing! I am in 4th grade and I love math, and since I am the smartest in my grade this video interested me a lot.

[@surusashikant6023]

I am in the fourth grade too.

[@surusashikant6023]

Very nice

[@bryannguyen8440]

This video helps me a lot and well explained

[@chuman5103]

my geometry teacher really be sending us things we learned in 6th grade like we in high school I know this