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Bada Bing
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ROOFCUTTER
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 Posted: Sat Sep 20, 2003 4:08 pm Post subject: |
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That is just spooky!
It is not always right but it is right way more than wrong! 
Good find Bada 
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KillerRoofcutter
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| Posted: Sat Sep 20, 2003 4:22 pm Post subject: |
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| ROOFCUTTER wrote: | That is just spooky!
It is not always right but it is right way more than wrong!
Good find Bada |
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Potato-VS-
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Location: Ontario Canada
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| Posted: Sat Sep 20, 2003 5:03 pm Post subject: |
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Arrrr! Its like a vending machine outside a cheap convience store... IT NEVER WORKS! I tried for like 10 min and its not getting one answer right.
<TVB>Potato-VS- |
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shockwave
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| Posted: Sat Sep 20, 2003 5:10 pm Post subject: |
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| Potato-VS- wrote: | Arrrr! Its like a vending machine outside a cheap convience store... IT NEVER WORKS! I tried for like 10 min and its not getting one answer right.
<TVB>Potato-VS- |
Actually it is using a simple mathematical formula to calculate what you are "thinking".
Suppose to choose a random two digit integer (10-99). Lets call this number xy, where x is the first digit and y is the second digit. The equation that it uses is xy-(x+y)=z. What you will find is that z is always a multiple of 9. I will solve it mathematically and using examples.
Math:
This will work for all integers.
We shall prove this for a 2-digit and a 5-digit integer.
X0, X1, X2 ... are single digit integers
A is an unknown integer
Z = (X0 * 1 + X1 * 10)
Z - (X0 + X1) = 9A
9X1 = 9A
X1 = A
Both are integers, so this is true.
Z = (X0 * 1 + X1 * 10 + X2 * 100 + X3 * 1000 + X4 * 10000)
Z - (X0 + X1 + X2 + X3 + X4) = 9A
9X1 + 99X2 + 999X3 + 9999X4 = 9A
X1 + 11X2 + 111X3 + 1111X4 = A
Example:
xy-(x+y)=multiple of 9
59-(5+9 )=45
58-(5+8 )=45
57-(5+7 )=45
56-(5+6 )=45
55-(5+5 )=45
54-(5+4 )=45
53-(5+3 )=45
52-(5+2 )=45
51-(5+1 )=45
50-(5+0 )=45
You can do more examples or have excel do them for you, but you will always find that the result is a multiple of 9.
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Potato-VS-
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| Posted: Sat Sep 20, 2003 5:20 pm Post subject: |
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Wow... All that math is like greek to me lol! I kinda get it. Thanks - I never actually knew that it was based on what you were thinking though it does make sense.
<TVB>Potato-VS- |
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shockwave
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Joined: 26 Feb 2003
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| Posted: Sun Sep 21, 2003 12:59 am Post subject: |
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| [WgD]Darude wrote: | ive seen this site b4 it goes by multiples of 9
and BTW shockwave please no more math it really hurts me to have to see math when im not in school  |
I am sorry, but I deal with math on a daily basis. So to me it is nothing at all.
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ROOFCUTTER
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| Posted: Sun Sep 21, 2003 9:05 am Post subject: |
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Hey Shockwave,
Could you give an example of how you would have Excell perform this?
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Only in America......do they have drive-up ATM machines with Braille lettering.
Last edited by ROOFCUTTER on Sun Sep 21, 2003 9:20 am; edited 1 time in total |
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Lil-Yugi
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shockwave
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| Posted: Sun Sep 21, 2003 10:56 am Post subject: |
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| ROOFCUTTER wrote: | Hey Shockwave,
Could you give an example of how you would have Excell perform this? |
I set excel up with 3 columns. The first cell (in the first column) put the number 11 (a starting point). I used the cell A1 for my first cell. The second cell (in the second column, B1) put the equation '=A1-INT(A1/10)-MOD(A1,10)'. This will do the xy-x-y part. The third cell with be a logical test if the xy-x-y is a multiple of 9. Put '=IF(INT(B1/9)=B1/9,"True","False")' in the cell C1. In cell A2 type 12. Now select cells A1 and A2. A small box appears at the bottom right of the selection. Drag that small box until A89. Now select cells B1 and C1. Drag them also down to row 89.
Finally just look at all the trues in the third column. If there are enough requests I will either email my excel file or post it somewhere.
[edit]I added an '=' to the first equation.[/edit] |
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DukeNukem
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| Posted: Mon Sep 22, 2003 1:40 pm Post subject: |
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Shocky lets approach this from a little different direction. Using the following notation we have a two digit number XY such that:
XY = (10*X + Y) where X & Y are in set of one digit integers [ i.e. {0,1,2, . . . 9} ]
Now then plug that straight into the equation that we are presented with and we have an equation for the unknown (call it Z):
XY - (X + Y) = Z
substitute for XY:
(10*X + Y) - (X + Y) = Z
now remove the parenthesis:
10*X + Y - X - Y = Z
collect like terms:
(10*X - X) + (Y - Y) = Z
the Y's cancel and leave:
10*X - X = Z
factor out X:
X(10 - 1) = Z
and do the number crunching [10 - 1 = 9] and we have:
9X = Z -- Q.E.D.
So we see that Y is irrelevant and the number is just 9 time the first digit. No need for an Excel table just multiply the ten's digit by nine and you have your answer.
Now go back to the link and notice that each time you restart the page that all the multiples of 9 have the same symbol, the one it shows when you click on the crystal ball.
So for those that said it was not right 100% of the time, you didn't do the math correctly, because it should never be wrong. DOH!!
P.S. This proof can easily be extended to any "n" digit number but the salient point is that it makes the value in the ones column totally irrelevent to the solution.
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omgshovelyouinthebutt?
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Joined: 06 Jul 2003
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Posts: 644
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| Posted: Mon Sep 22, 2003 2:27 pm Post subject: |
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If shocky can fix an air-e-o-plain than he wins 
and y=mx+b OMG.....////
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shockwave
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| Posted: Mon Sep 22, 2003 4:07 pm Post subject: |
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| DukeNukem wrote: | | Shocky lets approach this from a little different direction. Using the following notation we have a two digit number XY such that: |
please refer to my post on this thread: Sat Sep 20, 2003 5:10 pm
I described the exact way that you did this except i also did it for a 5 digit number, proving that you can do this for any positive integer not just 2-digit integers. |
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Kazebari
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DukeNukem
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| Posted: Mon Sep 22, 2003 4:42 pm Post subject: |
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| Shockwave wrote: | please refer to my post on this thread: Sat Sep 20, 2003 5:10 pm
I described the exact way that you did this except i also did it for a 5 digit number, proving that you can do this for any positive integer not just 2-digit integers. |
I had seen your proof, and I was not disagreeing with it at all. Since I too work with this kind of stuff all day, I didn't have any problem following it. But, I was including some of the steps that some others may not have followed.
The "difference direction" that I was refering to is that I did not start with the assumption that XY - (X +Y) =9A [where A is some integer]. Instead I solved directly to show that it is 9 times X. [NOTE: we were using Z for different things so that could be confusing to some]
What made me feel that some did not follow it in enough depth is that they were asking for a spreadsheet to calculate the values for two digit numbers. I was saying -- look it it is just the first (leftmost) digit times 9.
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