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Good afternoon, ladies and gentlemen,
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my name is Art Benjamin
and I am a "mathemagician".
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What that means is
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I combine my loves of math
-- or I should say Maths --
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and magic to do what I call mathemagics.
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But before I get started
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I've got a quick question for the audience
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By any chance, did anyone here
in the audience
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happen to bring with them
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this afternoon
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a calculator?
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If you have one, perhaps on your phone,
or somewhere,
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and you're pretty comfortable using it,
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raise your hand.
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I'll need a couple of people
to help me out here.
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I see one... two...
and perhaps one more...
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three. With the three of you,
bring out your calculators
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and join me up here on stage
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and let's give these volunteers
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a nice round of applause.
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Come on up.
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Great.
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Over on this side, please.
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Awesome.
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Now, since I have not had the chance
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to work with these calculators,
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I need to make sure
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that they are all working properly.
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Would somebody get us started
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by giving us a two-digit number, please?
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How about a two-digit number?
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Just yell one out.
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Oh, okay. That's fine! 74!
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And another...
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how about another two-digit number?
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How about on this side?
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39!
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Multiply 74 times 39 on the calculator.
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Make sure you get 2886
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or the calculators are not working.
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Do each of you get 2886?
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Give them a round of applause!
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Phew
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Now I noticed that took some of us
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a little bit of time to get the answer.
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That's ok.
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I'll give you a shortcut for multiplying
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even faster on the calculator.
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There's something called
"the square of a number"
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which, most of you know, is
taking a number
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and multiplying it by itself.
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For instance 5 squared would be...
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25.
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6 squared would be...
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36.
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73 squared would be...
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something else. Yeah...
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So on most of these calculators,
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they've little shortcut buttons
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that allow you to square numbers
even faster.
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What I'm gonna try and do
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is to square
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...and you might test it,
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make sure you could square 5 or 6 with it,
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but what I'm gonna try and do is
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to square in my head
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three two-digit numbers
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faster than they can do
on their calculators,
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even using the shortcut method.
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But I'll ask these three people
in the third row here,
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each yell out a two-digit number
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and if you would square the first one,
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the second,
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and the third one.
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I will try and race you to the answer.
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So quickly a two-digit number, please?
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24, great, next...
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What was that?
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98... and one more...
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26. Would you call out
your answers, please?
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576.
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9604.
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676.
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Give them a round of applause!
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Let me try to take this one step further.
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I'm going to try to square
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some three-digit numbers.
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This time, I won't even write these down.
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I'll just call them out as they're
called out to me.
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Anyone at the hall, call out
a three-digit number,
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anyone on our pannel, verify the answer.
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If I get the answer right,
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give me a big thumbs up,
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if I make a mistake,
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let me know and I'll try and fix it.
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A three-digit number, anyone?
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576 is 331,776...
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Yes? Good!
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How about another three-digit number, sir?
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103 is 10609, way too easy!
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Another three-digit number?
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125 is 15,625, but that's 5 to the 6th
power, so that was easy too.
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How about another three-digit number, sir?
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985 is 970,225.
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Yes, thumbs up?
closed TED
