The special nr 9

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daanopperman
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The special nr 9

Post by daanopperman »

Somewhere on then forum I read about the special no's 3 , 6 and 9 , sure it was a article!e about N . Tesla . To satisfy my curiosity I looked at it's " special " properties , and to my great relieve found the next .

To multiply by nine ,

The digets between 1 and 10 subtract 1
The digets between 11and 20 , subtract 2 and so forth .

We will subtract 2 numbers from the number we want to multiply with .

8 x 9 subtract 1 from 8 , that leaves 7 , the first diget from the answer .
Subtract 1 from 8 ( the second calculation ) = 7 , if we now subtract this no from the 9 we get 2 , the second diget for the answer .

21 x 9
- 3
18( now second working ) subtract 1 from the 1 of 21 ) = 0
If we subtract this 0 from 9 we have 9 , the second diget of the answer

18 + 9 = 189

222 x 9. Subtract 23
23
199 subtract 1 from the last diget 1 - 2 = 1 , now subtract this no from 9 = 8
That is the last diget from the answer .

1998

1 4 6 3 2 7 8 9 1 2 4 5 6 2 3 4 1 8 9 x 9
1 4 6 3 2 7 8 9 1 2 4 5 6 2 3 4 1 9
1 3 1 6 9 5 1 0 2 1 2 1 0 6 1 0 7 7 0 1. ( the last diget came from 1- 9 = 8 , 8 - 9 = 1)

See the relation between what we multiply with and what we subtract from that no .
We change only the 18 to 19 .(always only the 2nd and3rd diget from the end of the no
thus the 189 from the top row becomes 19 )

When multiplying with a diget that ends in a 0 , the 0 will just drop down into the answer ,we will not subtract 1 from the 0 .

3 5 0 x 9
Because the diget is between 350 and 360 we can only subtract 35

3 5 0 x 9
3 5
3 1 5 0. Here you can see the 0 just dropped down into the answer .

3 5 1 x 9
3 6
3 1 5 9 (1 - 1 = 0 , 0 - 9 = 9. We always subtract 1 from the last diget in the no we multiply with , this is a second calculation only on the last diget , always - 1 )


because 351 falls between 351 and 360 we have to subtract or change the
35 to 36


I therefore think it is possible to formulate a formula for the multiplication of the no 9 .

Only for those who are interested .

Daan .
daanopperman
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Post by daanopperman »

I see the pad has put everything on the margin line , must be a tampad .
daanopperman
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re: The special nr 9

Post by daanopperman »

To correct


58629461745 x9
--5862946175
527665155705
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