Need explanation from you mathematicians

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T_R_Oglodyte

Kay H said:
I know this must have some mathematical explanation but I don't get it but I'm math impaired. Mt DH who is very good with math problems can't figure it out either. Can anyone explain?

http://trunks.secondfoundation.org/files/psychic.sw8

No matter what two digit number you start with, your final answer will always be 9 or a multiple of 9. The key on the right is programmed to always return the same symbol for 9 and all mulitiples of 9, and to return that symbol as the answer. The entries for all numbers that are not 9 or a multiple of 9 are totally irrelevant.

You can work it out algebraically by letting your two digit number be xy where x = any digit from 1 to 9 and y = any digit from 0 to 9. Then just follow the steps. In the end, your answer will be 9*z, where z is another digit from 1 to 9.

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Kay H

TUG Member
Thanks, Steve. You answered me before I edited my post and corrected my link. You are fast. DH will appreciate your spped and explanation. He has been trying to figure it out for 3 days now.

Thanks again. I owe you a drink T_R_Oglodyte

Kay H said:
Thanks, Steve. You answered me before I edited my post and corrected my link. You are fast. DH will appreciate your spped and explanation. He has been trying to figure it out for 3 days now.

Thanks again. I owe you a drink I need to expand my answer a bit. My explanation is incomplete.

Your first number actually is 10X + y. For example, if you started with 23:
• x=2 and y=3.
• Then, 10*x + y = 10*2 + 3 = 20 + 3 = 23.

The problem tells you to add together the two digits and subtract them from the first number.

So, algebraically what you have is:

(10x + y) - (x + y).

That rearranges to x*(10-1) + (y-y)

which simplifies to 9*x.

Thus, the final answer will be 9 mulitplied by the first digit in your two digit number.

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T_R_Oglodyte

Kay H said:
Thanks again. I owe you a drink I think a McMenamins Hammerhead will be a bit difficult for you to pull off. Icarus

TUG Member
They had me going there for a minute, because when you click try again, the symbol table changes.

-David

T_R_Oglodyte

For the more mathematically inclined, you can do the same thing with a two-digit hexadecimal number, but then the resulting answer will be a multiple of 15 instead of 9.

More generally, if you use a numbering system of base n, the resutling answer will be a multiple of n-1. This is a basic property of numbering systems. In the days before calculators, there was a procedure for checking arithmetic calculations called "casting 9's", that exploited this same property.

I was taught number bases in fifth grade, and learned to cast 9's in base 6, base 8, and base 12. Of course in those number bases, you would casts 5's, 7's, and 11's, respectively.

Janette

TUG Member
See, all that math you were required to take does pay off. I love the beauty of algebra.

Kay H

TUG Member
T_R_Oglodyte said:
I think a McMenamins Hammerhead will be a bit difficult for you to pull off. Go ahead, Steve. Take advantage of a mathmatically impaired senior citizen  Actually, unbeknownst to me. DH sat down with a pencil and paper, sans math equasions and figured it out in 15 minutes before I asked here. He said I could have done the same thing (little does he know). You are waaaay too technical for my taste, but I guess I asked, didn't I.

TUG Member

Kay H

TUG Member   Clark said:
Kay dont let those math guys mess with your mind. I researched this pheonomena in detail about a year ago and published the *real* explanation in laymens terms at

http://www.canandaiguarotary.org/psychicexplanation.htm

When you read that, you will understand.
I may be mathmatically impaired but I'm not impaired. Nor gullible JudyS

TUG Member
Ah yes -- this was posted here a year or so ago. As I recall, there were a bunch of sites out there, all with the same basic trick.

Anyway, I love the sound effect!

Clark

TUG Member
Kay H said:
I may be mathmatically impaired but I'm not impaired. But you gotta admit, it's a good explanation --