Lightning calculation and other "mathemagic" | Arthur Benjamin 

I've never rooted so hard for someone to do a math problem.

"I know as a magician, we're not supposed to reveal our secrets, but I'm not too afraid that people are going to start doing my show next week" Classic!

This guy's pre-frontal cortex must be a quad-core.

teacher: no calculators allowed in tests me: brings arthur benjamin teacher:

Oh, the days before everyone had a calculator on their phones.

More than just impressive, he seems like a genuinely great guy, great humor.

A fantastic guy. Really deserves a standing ovation.

I just love this guy. He's incredible.

loved it when he showed no problems in revealing his methods. Amazing!! Dam good!!!

This guy is great! it's one thing to be a math genius...it's another to know how to work a crowd.Seriously, the way he keeps the audience enthralled and inserts light humour "Let me re-cap *puts cap back on*" is a great way to ease the audience.Wow. Great Going Art :)

What I liked about this that the guy was actually funny. You wouldn't expect it from this kind of person. Very good!

My sister has his "the Great Courses: The Secrets of Mental Math" She is absolutely amazing! She can finally square 5-digit numbers in her head, though it takes roughly 2-3 minutes.

this guy has to have that talent where he can remember every detail of his life

1:27 He almost said the word stupid

Saw this live today, he came to our school and he truly is amazing!!! Amazing work !!!!

It's a mind blowing application of the (a+b)^2 and (a-b)^2 formulas. Still a damn genius.

This man is banned from all casino's in the state of Nevada.

Nice viewing.. But two mistakes 457^2 = 208849 [Not 208549], 722^2 = 521284 [Not 513284] I guess the people with the calculators on stage doubted themselves / were embarassed to point it out. But still amazing to do this in so short a time.

I got the book. He's phenomenal!

My class invites you to our school. I have showed this video so many times to so many classes. Every year my students are amazed. Some of them say you are their idol because of your mental math skills.

Truly appreciate Arthur Benjamin's efficiency, intelligence and eloquence. Thanks for sharing this video. Best wishes.

Art, you rock! Art Benjamin is a professor where I went to college, Harvey Mudd College. Despite knowing him for years, I am still in awe at his mental math ability.

I was impressed... yes with "the show/ presentation" but more so, how fast my 2kids picked up mental math as a game. You gotta get this guys book! It makes math very "useful" for everyone. I wonder why schools have not picked up some of his methodology. It is so musch easier than how traditional math is tought. When you look past the showmanship of this video, there is real science, genious, and surprisingly FUN. Very impressive Mr. Benjamin. Best of luck to you.

Oops, I see a carry coming.

Interestingly, in the trick, 8649 is a multiple of 9 which means that any multiple of it will also be a multiple of 9. The test for divisibility for nine is that all the digits added will still give a multiple of 9 if done recursively and so we can just add the remainders with 9. (ie. 81(8+1) , 8649 ( 8+6+4+9 = 27, 2+7 = 9) . We don't have to even go this far in addition. We can keep subtracting 9 as the sum becomes greater than 9 and that's all he does with his showmanship of course, eg. He took 8649 because it was convenient, (he says six digits in "any order" because the order of the sum of the digits hardly matters. A middle school student knows this. person 1 -1,9,7,0,4,0 - (find the sum subtracting 9 every time the sum exceeds 9 and you get 3 - so the number to be added to this to reach 9 would be 6 and that's what he says. person 2 - 4,4,8,7,5,2 - circular sum = 3 therefore answer = 6 Person 3 - 0,7,9,0,4,4 - circular sum = 6 . Ans = 3 Person 4 - 2,6,3,9,7,2 - circular sum = 2. Ans = 7. Loved the way he pulled off a middle school question with all that showmanship.

I don't know if this is how he did the missing digits trick or if it was just a coincidence: the number he chose, 8649 is divisible by 9 and I know this because if you add all the digits, you get 27 which is 9*3. The is the divisibility rule for any multiple of 9. If you multiply 8649 by a 3 digit number, it will still be a multiple of 9 and thus the rule still applies. For example, if they told you that 6 digits were all 1's, then you would know that the last digit is a 3.

When he asked the audience what 5 squared was, I blurted out the wrong answer..

Wow, a standing ovation! Arthur Benjamin is really talented, and he's so great at adding humor to all of this! :)

Wow, amazing! He's well articulated, talented, and entertaining as hell.

This is so awesome, I am really at awe. I''ve bought his book before I saw this video, now I'm gonna read it

The first time I remember seeing this video was in my pre-calc class junior year of high school back in 2010-'11. The video is so good that I keep coming back to it now several years since I finished school.

He must have eaten a calculator when he is 1 year's old

This was amazing to watch. - Definitely not the same as this video, but sometimes I give my son math problems just on a whim to solve, and I gave him 97+49 ...He gave me the answer from his head before I could. :P He's 7. lol You would think I'd be embarrassed to tell that story, but nope. Too proud of him to care. :P If he's a natural mathematician, I will definitely support and encourage his development in that subject.

First I said: wow he is a math genius. Then I said: wow he is a time traveler.

Thousands still do it in India. Shakuntala Devi is a famous and much venerated Indian mathematician who is considered a genius and is popularly known as the Human Computer. In 1977, Shakuntala extracted the 23rd root of a 201-digit number mentally, 12 seconds faster than the Univac-1108. She even occupies a place on the 1995 Guinness Book of Records for her skills.

"someone give me a 3-digit number." "100."

Lol, same exact thing in another TEDx Talk

I actually watched this clip more than twice.

This guy is my math teacher at Mudd. He's awesome.

that standing ovation atlast gave me goosebumps

I get a hint this gentleman is good at maths. Just a hint though...

"let me re-cap"....... ahhaah lol nice one. XD

This show's script if identical to his Ted talk 5 years later it's almost insane. I can't believe he did the exact same show over and over for that long.

Wow This was the most incredible thing I've ever seen!!!! What a gift!!!!

8:00 For day of the week trick

I like him, he's so smart and funny as well!

AMZING!! just unbelievable! My math teacher also impressed!

Watched this in Math Club and my seat mate who was a fast calculator was mind-blown.

hax, VAC banned.

That was awesome! Wish I could just do the 2 digits in my head!! :)

I just saw his show in Kearney. It was the best show I've ever seen!

fantatic mindblowing,he has extrawordinery skills , and commond on the mathematics amazing

everybody in the audience are in on it.

I need him as my next math teacher...

He is great in mental math, there is no question about that. I had that experience when I was in grade 5 in China. wht i remember was doing addition and subtraction instead of multiplication, nothing very tricky, coz u still have to memorize all the procedures and number in it.

I just saw this guy on the Colbert Report lol He's pretty damn cool!

This is insane. I was actually going to bed. then I thought, lets watch a TED talk. I am fresh now. *Standing Ovation*

This guy shows some amazing abilities, but can he take out the trash ?

Agreed. Makes me wish I enjoyed algebra more in school.

Sounds right, These guys put so much work into a small tricks like this.

Me returns from grocery store Mom: where is the remaining money? Me: 13:56

A few weeks ago I attempted to multiply a 4-digit number by a 2-digit number... in my dream. I actually remembered my way of calculating it when I woke up and it was correct, but it wasn't finished, unfortunately

I'd love to see this live.

i was priviliged to see arty live a few times, he is very entertaining,

One mistake sir, 1824, June , 6th was actually sunny ⛅. Lol

His intro: Exact same wording he used at our assembly today. :O

I salute this man,,,he's so smart!

The people on stage don't know how to use their calculators. Even when he's wrong they say he's right. 457 ^ 2 = 208,849, not 205,849 722 ^ 2 = 521,284, not 513,284 He did square the four digit number correctly. I'm impressed.

Mother of MATH !!!!!!!!!!!!!!

at 3:42 he made a mistake... 457^2 is 208849 and not 205849 as he said!

How am I JUST seeing this!?! He's not only Brilliant, he's HILARIOUS! Thank you Arthur Benjamin!

Although I typically frown strongly upon the typical math magic I've seen, I can't help but appreciate the work that this man does and the show that he puts on. Numbers are simple, and with practice, observation, and motivation, It's not surprising that this can be done. There are many unobserved patterns and unpopularized formulas that can make these calculations relatively simple. I am not surprised, and barely impressed, but I am very appreciative of the interest and practice behind it all.

what happened to cookie though .did anyone eat it🤭🤭🤭

He just visited our school! :D AMAZINGGG

Just awesome.

This guy is so good. Definitely, definitely.

No magics just mathematics.

"It will take me a little bit of time" it would take me a year.

this is Amazing!

Na, you can easily calculate all the stuff he was doing. The day of the week trick is very easy to learn, took me like 4 hours of practice when i was 7 years old. SUPER awesome bar trick :)

722^2=521284 and not as he claimed 113284 4:01

What if someone had left out 0 or 9?

this is beyond cool! i so respect this guy, he has an amazing talent that he must have worked at for a long time. kudos to him

Spectacular!

why no one ever pick zero?

damm killer cpu

lol, "cookie fiscient...i see a carey coming..."XD, we watched that in our English class. The whole classed was totaly stunned.

Incredible

he is a human calculator nothing beats him

my math teacher was in a conference with Arthur Benjamin and beat him at the 24 game

Utterly incredible

Incredible.

I am pretty decent at squaring 1 digit numbers in my head myself :)

3:41 he's asked about 457*457 and he says 205,849... btut it's actually 208,849

Mine did too. Love this guy

the answer for 722 squared was actually wrong.

Woow this genius Hope he swallowed a scientific calculator.....love from Kenya.

as a senior in high school, i can also tell you that your typical high school that all the middle-aged people have grown up in, has been in a single word, disintegrated. Im top of my class at conrad weiser high school, and this has not hindered my ability in any way.. Im a nerd, proud to be one.. There's a saying, "you can call me nerd today, but boss tomorrow." Girls know this too.. @Oli978Oli978

He did pretty much the exact same thing in a Ted (might have been TedX) talk many years later. Same words and everything, just different numbers haha

okay then mr genius, tell me what is 1+1 ?