good morning ladies and gentlemen my name is art Benjamin and I am a
mathematician what that means is I combine my love's of math and magic to
do something I call mathemagics but before I get started I have a quick
question for the audience by any chance did anyone happen to bring with them
this morning a calculator seriously if you have a calculator with you raise
your hand raise your hand I was your hand go up now bring bring it out bring
it out anybody else i see i see one way in the back you serve that that's three
and anybody on this side here okay you over there on the iowa the four of you
with calculators please bring out your calculators then join me up on stage and
let's give these volunteers a nice round of applause now since i haven't had the
chance to work with these calculators i need to make sure that they are all
working properly would somebody get us started by giving us a gay two digit
number please how about a two digit number 22 and another two-digit number
sir multiply 22 x 47 make sure you get 1034 or the calculators are not working
do all of you get 1034 1034 594 let's give three of them a nice round of
applause there would you like to try a more standard
calculator just in case okay great what I'm going to try and do them I noticed
that took some of you a little bit of time to get your answer that's okay i'll
give you a shortcut for multiplying even faster on the calculator there's
something called the square of a number which most of you know is taking a
number and multiplying it by itself for instance 5 squared would be 25 now the
way we can square on most calculators let me demonstrate with this one is by
taking the numbers such as five hitting times and then equals and on most
calculators that will give you the square on some of these ancient rpn
calculators you've got an x squared button on it allow you to do the
calculation even faster what I'm going to try and do now is to square in my
head for two digit numbers faster than they can do on their calculators even
using the shortcut method what I'll use is the second row this time I give four
of you 1234 to each yell out a two-digit number and if you would square the first
number and if you would square the second the third and the fourth I will
try and race you to the answer okay so quickly a two-digit number please 30 7
squared okay 23 squared okay 59 squared okay and finally 93 squared would you
call out your answers please 1369 529 3481 thank you very much
let me try to take this one step further going to try to square some three-digit
numbers this time I won't even write these down i'll just call them out as
they're called out to me anyone i point to call out a three-digit number anyone
on our panel verify the answer just give some indication if it's right a
three-digit number sir yes 987 squared is 970 4169 yes good another another
three digit another another three digit number sir 457 squared is 205,000 849
2058 49 yes again another another three digit number sir 321 is 100 3041 1030 41
yes one more three digit number please 722 is 500 well that's a harder one said
um 513 thousand 284 yes what one will one more three digit number please 162
squared is twenty 6244 thank you very much
let me try to take this one step curtain I'm going to try to square a four-digit
number this time now you can all take your time on this I will not beat you to
the answer on this one but I will try to get the answer right to make this a
little bit more random let's take the fourth row this time let's say one two
three four if each of you would call it a single digit between 0 and 9 that will
be the four-digit number that I'll square 975 89 758 this will take me a
little bit of time so bear with me 95 million 218,000 564 thank you very much
now I would attempt to square a five digit number and I can but unfortunately
most calculators cannot eight digit capacity don't you hate that so so since
we've reached the limits of our calculators what's that does yours go
cuz yours go higher oh you wouldn't yours does I'll talk to you later hey in
the meanwhile let me conclude the first part of I show by doing something a
little trickier let's take the largest number on the board here eight six four
nine we do each enter that on your calculator and instead of squaring it
this time I want you to take that number and multiply it by any three digit
number that you want but don't tell me what you're multiplying by just multiply
it by any random three digit number so you should have as an answer either a
six digit or probably a seven-digit number how many digits do you have six
or sep seven and yours 77 and uncertain 7 is there any possible way that I could
know what seven digit numbers you have say no good then I shall attempt the
impossible or at least the improbable what I'd like each of you to do is to
call out for me any six of your seven digits any six of them in any order
you'd like one digit at a time I shall try and determine the digit you've left
that so starting with your 7 digit number sign applaud any six of them
please did you leave out the number 6 good okay that's one you have a
seven-digit number called any six of them please I think I learned heard five
numbers for if I went four for 875 did you leave out the number six same as she
did okay you've got a seven digit number called any six of them loud and clear I
think you left out the number three that's three the odds of me getting all
four of these right by random guessing would be one in ten
10 to the fourth power ok any six of them really scramble them up this time
please you do you got the number seven and let's give all four of these people
a nice round of applause thank you very much
for my next number while I mentally recharge my batteries I have one more
question for the audience by any chance does anybody here happen to know the day
of the week that they were born on if you think you know your birthday raise
your hand let's see starting with like start with a gentleman first okay sir
what year was it first of all that's why start with gentleman person what year
nineteen fifty three in the month november what 23rd was that a monday yes
good somebody else who else would like to i don't have to see anything woman's
handsome i guess how much you want year nineteen forty nine in the month october
what fifth was that a wednesday yes my i'll go way to the back right now how
about you yell it out what year nineteen fifty-nine ok on the month februari what
six was that a friday good how about person behind her ha ha what year was it
1947 and the month may what seventh was that be a wednesday yes thank you very
much
ah anybody here who liked to know the day of the week they were born we could
do it that way corfu of course I could just make up an answer and you would
enough so I come prepared for that I brought with me a book of calendars goes
as far back into the past as 1800 cuz you never know I didn't mean to look at
you sir you were just sitting there ah anyway Chris you can help me out here if
you wouldn't mind this is a book of calendars and Alaska who wasn't the
wanted to know their birthday you sir okay but what year was it first of all
66 turned to the calendar with 1966 and and what month April what 17th I believe
that was a Sunday can you confirm Chris yeah okay I'll tell you what Chris as
long as you have that book book in front of you do me a favor turn to a year
outside of the 1900s either in the 1800s or way into the 2000s that'll be a much
greater challenge for me what your Chris would you like 18-24 1824 okay and what
month June June what 66 was that a Sunday it was and it was cloudy good
thank you very much
but I'd like to wrap things up now by alluding to something from earlier in
the presentation there was a gentleman up here who had a 10 digit calculator
where is he would you stand up a 10 digit guy okay uh well stand up for me
just for a second so I can see where you are okay okay you you you have a 10
digit calculator sir as well okay what I'm going to try and do is to square in
my head a five digit number requiring a 10 digit calculator but to make my job
more interesting for you as well as for me I'm going to do this problem thinking
out loud so you can actually honestly hear what's going on in my mind while i
do a calculation of this size now i have to apologize to our magician friend
Leonard Green 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 so I
think we're okay
so let's see let's take a let's take a different row of people starting with
you the I'll get five digits 1 2 3 4 that did this role right let's do the
row before you sorry you sir 1 2 3 4 5 called a single digit that will be the
five digit number that i will try to square go ahead 5768 350 7683 squared
yuck let me let me explain to you how I'm going to attempt this problem I'm
going to break the problem down into three parts I'll do 57,000 squared plus
683 squared plus fifty seven thousand times 6 83 times to add all those
numbers together and with any luck arrive at the answer now let me recap
thank you while I explain something else I know that you can use right huh Brett
around while I do these calculation you might hear certain words as opposed to
numbers creep into the calculation let me explain what that is this is a
phonetic code a mnemonic device that I use that allows me to convert numbers
into words I store them as words and later on retrieve them as numbers I know
it sounds complicated it's not I just don't want you to think you're seeing
something out of rain man here there's definitely a method to my madness
definitely definitely sorry you want to talk to me about ADHD afterwards you can
talk anything um by the way one last instruction for my judges with the
calculators okay you know who you are there is at least a fifty percent chance
that i will make a mistake here if i do don't tell me what the mistake is just
say your clothes or something like that and i'll try and figure out the answer
which could be pretty entertaining in itself if however i am right whatever
you do don't keep it to yourself okay make sure everybody knows that i got the
answer right because this is my big finish okay so without any more stalling
here we go I'll start the problem in the middle of 57 times 683 now 57 x 68 is
thirty-four hundred plus 476 is 3876 has 30 8760 plus 1 71 38,000 761 17 is
thirty-eight thousand nine thirty one thirty eight thousand nine thirty one
doubled out to get 77,000 862 77,000 862 becomes cookie efficient cookie fishing
is 77,000 822 that seems right I'll go on cookie fishin okay next ID 57 squared
which 3249 so i can say three billion take the 249 and that took cookie 249
oops but I see a Carrie coming to 49 I that's a cookie to fifty plus seventy
seven is 327 million fish and fishin ok finally we do 683 squared that's 700
times 666 plus 17 squared is 466453
to get oh she 328 thousand 489 good thank you very much i hope you enjoy
good thinking
you