Faster than a calculator | Arthur Benjamin | TEDxOxford

At recess I will be very happy to tell you. Now, there's only a little bit of time left, so I'd like to do something else that I mentioned earlier when we had the

calculator

s on stage. I will try to square a five-digit number, which requires a

calculator

with ten or more numbers. Feel free to get out your calculators right now. But to make my task more exciting for both you and me, I'll solve this last problem by thinking out loud, so you can hear what's going on in my mind as I perform a calculation of this magnitude.

Let's create a five-digit number. Why don't we ask the person here in this hallway, the five people on the other side of this hallway, to each give me a number, which would give a five-digit number? three. Seven. six. nine. One. 37,691 per square, that's exciting! Let me explain how I will solve this problem. I will divide the problem into three parts. I will square the number 37,000, plus the square of 691, plus the number 37,000 multiplied by 691 multiplied by two. Add these numbers together and you will get the answer. Now let me explain something else to you. As I do this calculation, you may hear some words, instead of numbers, enter the calculation.

Let me explain to you what it is. It is a verbal code, a mnemonic aid that I use. It gives me the opportunity to convert numbers into words. I store them in the form of words and then retrieve them in the form of numbers. I know it sounds complicated, but it's not. I don't want you to think that you'll see anything "extraordinary powers" here. (Laughs) There is definitely some method to this madness, of course, of course. I'm sorry. (Laughs) The latest guidelines for referees with calculators. Now, who has the answer from the beginning? Raise your hands.

Well, that's enough. There is a 50% chance that you will make a mistake in this matter. If I make a mistake, don't tell me what's wrong, just say, "You're close or something" and I'll try to figure it out, which will be a lot of fun in itself. But, if I'm right, whatever you do, don't keep it to yourself. Make sure everyone knows I got it right, because it'll be the grand finale, okay? So, without further ado, let's get started. I'll start by solving the problem in the middle, 39 times 691. Now, let's see, oh my goodness, so it's 700 minus 9.

I'll take advantage of that, 700 times 37 is 25,100. 37 times 9 is 333. Subtract the two results to get 25,567. 25,000 - I think so? Yes - 25,567. We double it to get 51,134. - 51,134 Okay, 51,000 is late tomorrow, late time tomorrow is 51,134 That sounds good, I'll follow up. Next, I go to square 37, which is 1369, so I can say a billion. Take 369 and add it to the light. will you be??? We add 369 to the light to obtain 420 million. Tomorrow, tomorrow, okay. Next we square the number 691, which is 700 times 682, plus the square of 9, the result is 477,481. Mat, if you need it, Mat, take 477. Shall we add it to tomorrow to get 611,481?

Audience: Yes! (applause). Arthur: Yes, good. Thank you very much to all. I hope you enjoyed the magic of mathematics. I'm Arthur Benjamin. thank you so much. (applause)