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John Cowne

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These are two of my favourite magical numbers: 793.8 and 1089. What's yours?
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SamtheNotsoMagnificent

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I guess I don't understand this question....
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Alan Smithee

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I don't think I understand the question either. So that makes 3.14 of us.

1089 seems familiar though....I think Radio 2 broadcasts on that frequency. Or did once upon a time.
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SamtheNotsoMagnificent

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Quote:
Originally Posted by Alan Smithee
I don't think I understand the question either. So that makes 3.14 of us.

1089 seems familiar though....I think Radio 2 broadcasts on that frequency. Or did once upon a time.


Penguin publishes a book titled 793.8, which is about presentations in magic by Jeff Stone.

Is that the reference?

EDIT: I also found this - 

1089 is widely used in magic tricks because it can be "produced" from any two three-digit numbers. This allows it to be used as the basis for a Magician's Choice. For instance, one variation of the book test starts by having the spectator choose any two suitable numbers and then apply some basic math to produce a single four-digit number. That number is always 1089. The spectator is then asked to turn to page 108 of a book and read the 9th word, which the magician has memorized. To the audience it looks like the number is random, but through manipulation, the result is always the same. It is this property that led University of Oxford mathematician David Acheson to title his 2010 book '1089 and all that: a journey into mathematics'.[3]

In base 10, the following steps always yield 1089:

  1. Take any three-digit number where the first and last digits differ by 1 or more.
  2. Reverse the digits, and subtract the smaller from the larger one.
  3. Add to this result the number produced by reversing its digits.

For example, if the spectator chooses 237 (or 732):

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Anthony Vinson

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798.3 is the Dewey Decimal designation for the nonfiction section that includes magic tricks. Many of us found our magical footing there, and will never forget the experience. Yeah, being a Boomer had its advantages!

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markd2990

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Quote:
So that makes 3.14 of us.


That's eff'ing hilarious! It made me spit milk out my nose while I was eating pie. [smile]
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RayJ

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Quote:
Originally Posted by Anthony Vinson
798.3 is the Dewey Decimal designation for the nonfiction section that includes magic tricks. Many of us found our magical footing there, and will never forget the experience. Yeah, being a Boomer had its advantages!

Av 


Yep, I'm a boomer too! You can add a letter to it also. So Q798.3 would be the books that are too tall to fit on a standard library shelf. They are on their own shelves, grouped with other "oversized" books. I believe the Q stands for Quarto.
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RayJ

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I'll add the numbers 3, 4 and 52. The latter is obvious, but good things come in 3s and you "usually" use 3 cups and 3 balls, I perform a 3 ring routine and there are tons of examples where 3 reigns its head like 3-Fly. 4 for four ace tricks, three balls and a shell, etc., etc..
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chris w

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Should you accidentally end up at 798.3 rather than 793.8, like Anthony and Ray, Google reports that you will be looking at books concerning equestrian sports and animal racing. Fun fact.

As a non-Boomer, I also had the experience of haunting section 793.8 at the local library.
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RayJ

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[QUOTE=chris w]Should you accidentally end up at 798.3 rather than 793.8, like Anthony and Ray, Google reports that you will be looking at books concerning equestrian sports and animal racing. Fun fact.

As a non-Boomer, I also had the experience of haunting section 793.8 at the local library.[/QUOTE

So 793.8 if you're serious about magic but 798.3 if you're just horsing around?
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SamtheNotsoMagnificent

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I'm from a small town. When they loaned out its book, the library closed until it was returned.
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Alan Smithee

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Quote:
Originally Posted by SamtheNotsoMagnificent
I'm from a small town. When they loaned out its book, the library closed until it was returned.


Hmm....

If the book is out on loan, and the library is closed, how was it possible to return it?

[smile] [wink]
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Alan Smithee

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Quote:
Originally Posted by RayJ
I'll add the numbers 3, 4 and 52. The latter is obvious, but good things come in 3s and you "usually" use 3 cups and 3 balls, I perform a 3 ring routine and there are tons of examples where 3 reigns its head like 3-Fly. 4 for four ace tricks, three balls and a shell, etc., etc..

My memory is not what it was, but I've got half an idea that there's some sort of card trick that uses three cards.

And to "add" another number isn't there something that uses 21 cards?

Or am I dreaming again?
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mac1054

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Reply with quote  #14 
1 and 2. One in the hand & two in the pocket.
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Alan Smithee

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SIX Card Repeat.

ELEVEN Card Trick: Edward Victor and Derek Dingle.

TEN and TWENTY Countback Force

E-Y-E Edward Victor again. Three cards.
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Mike Powers

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Reply with quote  #16 

 

Quote:

In base 10, the following steps always yield 1089:

  1. Take any three-digit number where the first and last digits differ by 1 or more.
  2. Reverse the digits, and subtract the smaller from the larger one.
  3. Add to this result the number produced by reversing its digits.

For example, if the spectator chooses 237 (or 732):



The above get you to 1089 which has it's own merit.

The underlying principle is more general than this if you want to force 9.

1. Take any number and
2. rearrange the digits in any order
3. Subtract the smaller from the larger
The result will be a multiple of nine. This means that the digits will add up to a multiple of 9. You don't necessarily get 1089 but if you keep adding the digits, you'll get to 9 eventually.

E.G. 43691 and 91364 (a rearrangement of 43691). So 91364-43691 = 47673 which is a multiple of 9 (it's 9*5297),
The digits of this result i.e. 47673 will add to a multiple of 9. In this case they add to 27. Then 2+9 add to 9. You can always get to 9 by this method.

There's a trick in TESSERACT that uses this principle starting with a five card poker hand (all number cards).

Mike

 

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John Cowne

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Reply with quote  #17 
Quote:
Originally Posted by RayJ
Should you accidentally end up at 798.3 rather than 793.8, like Anthony and Ray, Google reports that you will be looking at books concerning equestrian sports and animal racing. Fun fact.

As a non-Boomer, I also had the experience of haunting section 793.8 at the local library.[/QUOTE

So 793.8 if you're serious about magic but 798.3 if you're just horsing around?
You’ve identified the librarian’s dilemma, Ray: where do you classify ‘How to make a racing horse disappear?’. For me, libraries and bookstores are some of the most magical spots on earth. A lesson learnt by me from all you guys here; although ‘re-arranging’ digits can sometimes be dangerous, it can also lead to fun-filled serendipity.
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John Cowne

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Reply with quote  #18 
Quote:
Originally Posted by Mike Powers

 



The above get you to 1089 which has it's own merit.

The underlying principle is more general than this if you want to force 9.

1. Take any number and
2. rearrange the digits in any order
3. Subtract the smaller from the larger
The result will be a multiple of nine. This means that the digits will add up to a multiple of 9. You don't necessarily get 1089 but if you keep adding the digits, you'll get to 9 eventually.

E.G. 43691 and 91364 (a rearrangement of 43691). So 91364-43691 = 47673 which is a multiple of 9 (it's 9*5297),
The digits of this result i.e. 47673 will add to a multiple of 9. In this case they add to 27. Then 2+9 add to 9. You can always get to 9 by this method.

There's a trick in TESSERACT that uses this principle starting with a five card poker hand (all number cards).

Mike

 

And to extend the possibilities, with Harry’s memory system, you could have a small (for Harry and the motivated - a large) library of books that you can let your spectator freely select from. I’m finding more and more that Magic is good for the boomer’s brain.
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Harry Lorayne

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Reply with quote  #19 

    Wanna' really get into numbers...check out my book, MATHEMATICAL WIZARDRY … effects with numbers that will make your audience think you're a mathematical genius.  Check it out (even order it) at harryloraynemagic.com .
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John Cowne

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Quote:
Originally Posted by Harry Lorayne

    Wanna' really get into numbers...check out my book, MATHEMATICAL WIZARDRY … effects with numbers that will make your audience think you're a mathematical genius.  Check it out (even order it) at harryloraynemagic.com .
Classics #5 is on my Christmas/birthday wish list; looking forward to it.
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SamtheNotsoMagnificent

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Quote:
Originally Posted by Alan Smithee


Hmm....

If the book is out on loan, and the library is closed, how was it possible to return it?

[smile] [wink]


It was a small town and you went to the police station. The librarian was also the chief of police. Lord help you if you got pulled over with an overdue book.
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Harry Lorayne

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Reply with quote  #22 
   
    John:  Running out of them. Shall I put one aside for you?
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RayJ

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Quote:
Originally Posted by SamtheNotsoMagnificent


It was a small town and you went to the police station. The librarian was also the chief of police. Lord help you if you got pulled over with an overdue book.


So if you got into trouble they'd really throw the book at you!
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Alan Smithee

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Who looked after the cop shop when the chief went over to the library?

[smile][wink]
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Alan Smithee

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Quote:
Originally Posted by RayJ


So if you got into trouble they'd really throw the book at you!


At the very least you'd get a ticket. A library ticket, perhaps?

With that you could borrow the book they throw at you and when it was due back, go and see the chief and.....ever onward.
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John Cowne

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Quote:
Originally Posted by Harry Lorayne
   
    John:  Running out of them. Shall I put one aside for you?
My wife said, “Great sales pitch, let’s get it!” So yes, please.. going to your site now. And DONE!😁
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Robin Dawes

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Reply with quote  #27 
My favourite magical number is 1001
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Robin Dawes

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Quote:
Originally Posted by SamtheNotsoMagnificent

...

It is this property that led University of Oxford mathematician David Acheson to title his 2010 book '1089 and all that: a journey into mathematics'.[3]
...


Also because it is a play on the title of a famous (and very funny) parody of British History textbooks by Sellars and Yeatman called "1066 and All That"
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SamtheNotsoMagnificent

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Reply with quote  #29 
Quote:
Originally Posted by Alan Smithee
Who looked after the cop shop when the chief went over to the library?

[smile][wink]


The fry cook. The local police station was the third booth on the right at the diner. City hall was in first and parks and maintenance was at the lunch counter. The outhouse out back was converted to a library when the diner got indoor plumbing.
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MagikDon

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42.........It is the answer to Life, the Universe and Everything! 

(Douglas Adams-Hitchhikers Guide to the Galaxy)   😃

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Alan Smithee

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"1001" is a carpet cleaner. It cleans a big big carpet for less than half a crown.
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Robin Dawes

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Reply with quote  #32 
1001 is also the number of nights that Scheherazade told tales to the Sultan so that he would not have her killed ... the magical tales we know as the Arabian Nights.

But it's my favourite magical number for a different reason.   It enables a very wonderful bit of simulated lightning calculation.  I always perform this at the start of my university course on Discrete Math:

Ask your audience for a three-digit number.  Tell them that to "make things harder" you will combine the number with itself to make a six-digit number.  So if they give you the number 783, you write on the board 783783.

Stare at the number and mutter under your breath, then cry out "13!  That number divides by 13 - someone check it on their calculator (or phone)" ... and you are right!

"Again!"  you say.  Another three-digit number is given ... say 166.  You write 166166 on the board.  This time it seems easier - you immediately call out "7!  It divides by 7. Check it!"  and you are right again.

"One more, and make it tough" you demand.  The audience offers 471.  On the board goes 471471.  You stare.  You mumble.  You point at the digits in confusion ... and yet in just a few seconds you catch your breath and state loudly and clearly "141 ... no wait, 143!  That divides by 143!"   And you are right again.

Of course it is all a scam.  My hat is off to those who can actually do impressive mathematics in their heads, but that's not what is happening here.  It turns out that if you take ANY three digit number and make it into a six-digit number by writing it after itself, it will ALWAYS divide by 13, and by 7, and by 143.

Here's why:   think of the original number as "abc" , so the extended number is "abcabc".  But "abcabc" = "abc"*1001  (eg 166166 = 166*1001)

And 1001 = 7*11*13.   So since 1001 divides "abcabc", we know 7, 11, 13 divide "abcabc" too ... and so do 7*11 = 77, 7*13 = 91, and 11*13 = 143.

This was discovered long ago by a mathematician named Booth.

But wait, there's more!  If the number is even, then it divides by 2 ... which means it also divides by 14, 22, 26, 154, 182 and 286.

If the digits of the number sum to a multiple of 3, then it divides by 3 ... which means it also divides by 21, 33, 39, etc.

If the last two digits are a multiple of 4, then the whole number divides by 4 ... which means it also divides by 28, 44, 52 and so on

With just a bit of practice you can pull off really astonishing feats of apprarent mental arithmetic.

You can do the same thing with four digit numbers, because 10001 = 73*137    So if we convert a four-digit number "abcd" to "abcdabcd", the result divides by both 73 and 137.  When I do this stunt in class I usually end with one demonstration on a four-digit number then claim my brain is all warmed up and we can start the class.

For the four-digit demo I don't name both 73 and 137 as divisors - I think that doing that would lead people (particularly math/computing students) to the answer too easily.

In fact you can find the factors of lots of numbers of the form 10...01 and you can do the routine with any of them.  I like using 1001 and 10001.

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