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·I'm listening if anyone can tell me how this works?????

http://www.mysticalball.com/ oo: oo: oo: oo: They didn't predict the tsunami. :bawling:

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I'm listening if anyone can tell me how this works?????

http://www.mysticalball.com/ oo: oo: oo: oo: They didn't predict the tsunami. :bawling:

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3,263 Posts

nope that isnt it

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3,263 Posts

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6,170 Posts

99 18 gives 81

88 16 gives 72

87 15 gives 72

5x gives 45

4x gives 36

etc etc etc

all multiples of 9 have the same symbol, click and that symbol changes. but all multiples of 9 have the same smybol still

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6,167 Posts

I guess sheer calculation power- but there must be a system.

You can group several combinations which always have the same result.

e.g. 13: 13-4=9

15: 15-6=9

Next one is 18, next one 27... see the system?

Ok, now why?

Take 23 and 32: one result is 18, the other one 27.

The 20.29s:

20: 2 kept steady. you always substract 2.

now oh wonder. 20 - 2 = 18.

add anything to 20, like 5: you also add it to what you substract. so even at 29 you calculate:

29 - 11 = 18.

so at the 30s you calculate:

3x-(3+x)

which is 3*10 + x*1 -3 -x = 30 -3 +x -x = 27.

wohoo, got the system.

so the last part is:

why is x*10 - x = 9*x?

well, except knowing the little x*9 and see it you can do prove it by complete induction:

assume that x*10 - x = 9 * x

start with x = 1:

1 * 10 - 1 = 10-1 = 9 = 9 * 1 True

continue with x-> x+1:

(x+1) *10 - (x+1) = (x+1)*9. True.

That means: this rule is true for all numbers!!!

E.g. be x = 1774:

1774 * 10 = 17740 - 1774 = 15966 = 9 * 1774

Hooray.

And the last line of my little proof explains also why:

10*x is x+x+x+x+x+x+x+x+x+x (10 times)

when you substract one x you get:

x+x+x+x+x+x+x+x+x (9 times) which is 9*x

:tongue:

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6,167 Posts

But now you should also know WHY its a multiple of 9 :grin:

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6,167 Posts

x,y := 1..9

xy = x*10 + y

xy - (x+y) = x*10 - x +y -y = x*10 -x = x*9

That means y doesn't affect the result, which is always the first digit times 9.

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6,170 Posts

it must have taken you about an hour to write that, and 10 seconds to think it up. Im far to lazy to explain the theory behind it :lol:

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3,263 Posts

the answer is always 9 or a multiple of 9

99 18 gives 81

88 16 gives 72

87 15 gives 72

5x gives 45

4x gives 36

etc etc etc

all multiples of 9 have the same symbol, click and that symbol changes. but all multiples of 9 have the same smybol still

[/ QUOTE ]

Basically what I said in a somewhat less technical way.

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6,170 Posts

looking at what you said, you're right, but in a far less technical way then SS's thesis

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6,170 Posts

whats your major? :lol: :waytogo:

whats your major? :lol: :waytogo:

[/ QUOTE ]

Underwater basket weaving....

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6,170 Posts

poli sci eh? or econ? :tongue: :lol:

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