# [111,111,111] x [111,111,111] =

Discussion in 'Physics & Math' started by Zardozi, Oct 16, 2007.

1. ### ZardoziIsvara.... . 1S Evil_LauRegistered Senior Member

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443
12345678987654321

derfeltGesp!

3. ### NeonBlackRegistered Member

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28
This is neat, but really not too surprising.

Because you used the brackets and X for multiplication, I first thought you meant the vector 111x+111y+111z crossed with itself. You really shouldn't do that.

5. ### devireRegistered Member

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79
11 * 11 = 121

111 * 111 = 12321

1111 * 1111 = 1234321

....

you get the picture.

7. I thought it was cross product too.

8. ### temurman of no wordsRegistered Senior Member

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1,330
I thought it was tensor product.

9. ### Learned HandRegistered Senior Member

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361
I'm not that much of a math whiz to even know "cross product" vs. product; so I thought it was 12345678987654321.

Guess sometimes the simplest answer is the right one, eh?

10. ### CyperiumI'm always meValued Senior Member

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3,000
Hmm...but why?

22*22 gives 484

so the reason perhaps why it doesn't work in larger numbers than 1 is because the number that would follow would be >9 and thus starting to mess up the rest of the numbers...

so 222*222 can't give 48(12)84 =) but instead yields 49284 (the "1" in "12" simply adds to the 8, leaving the 2 behind)

Last edited: Oct 21, 2007
11. ### invert_nexusZe do caixaoValued Senior Member

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9,686
Because of the way the ones stack up.

011
011
-----
11
011
-----
121

Pretty simple really.

Interesting though.

12. ### superluminalI am MalcomRValued Senior Member

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10,876
I thought it was a WalMart product.

13. ### CyperiumI'm always meValued Senior Member

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3,000
Oh kay

, as you can see in my above example it does work on larger numbers than one, but it scrambles it a bit

14. ### invert_nexusZe do caixaoValued Senior Member

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9,686
Yes.
In fact, 111,111,111 is the highest number it will work with. Add one more one and it screws up the works because you have to start 'carrying the one'.

15. ### MetaKronRegistered Senior Member

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5,502
Use a larger base.

16. ### TruthSeekerFancy Virtual Reality MonkeyValued Senior Member

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15,162
Mathematics are filled with tons of symetries like this one.

Ever heard of the guy who teaches kids how to multiply and divide really large numbers at an amazing speed?

17. ### CyperiumI'm always meValued Senior Member

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3,000
Yes, how does that work?

If someone knows, it would be great if you taught us, isn't that what sciforums is all about anyway?

18. ### TruthSeekerFancy Virtual Reality MonkeyValued Senior Member

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15,162
Sorry to disappoint you, but I don't remember how the guy did it.... :shrug:

One trick that I do always use when I don't have a calculator is dissecting the numbers, making them all multiples of 10. Like this...

1430=

1000
400
30

Then I do the calculation. For instance, a simple one: 1430 / 2

1000/2 = 500
400/2 = 200
30/2 = 15
sum = 715

Sometimes I do faster shortcuts too. Like this:

1400/2 = 700
30/2=15
sum=715

19. Also, if you are attempting to calculate numbers that are multiples of 111, you can use 37 multiplications, and raise it by a factor of 3 each time so...
111= 3 x 37
222= 6 x 37
333= 9 x 37 ect. ect. ... ... ...

Well, there's my peice anyway.

20. ### TruthSeekerFancy Virtual Reality MonkeyValued Senior Member

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15,162
That's exactly the kind of trick I've discovered one time. While I was watching the Butterfly Effect, for some bizarre reason. That movie makes my brain behave in a very strange manner... :bugeye:

21. ### CyperiumI'm always meValued Senior Member

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3,000
That's nice.

When multiplying something *5 like 2398 * 5, you can take (2398/2) * 10 instead. Using your technique together with mine we get:
2000/2 = 1000
300/2 = 150
90/2 = 45
8/2 = 4
2398/2 = 1199
1199 * 10 = 11990

So 2398 * 5 = 11990

Easier example is 5 * 26, it's 130 since 26/2 = 13 and 13 * 10 is 130.

This also works when multiplying with *15, like 230 * 15, first you take 230 * 10 which is 2300, then you take 2300/2 = 1150, and add them 2300 + 1150 = 3450, so 230 * 15 is 3450

Last edited: Oct 22, 2007
22. ### TruthSeekerFancy Virtual Reality MonkeyValued Senior Member

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15,162
23. I remember what was a godsave when i was in primary school. We were always taught that the 9x table had a particular design to it... sure you all know it... we were all taught it at some point...
9x1=9
9x2=18
9x3=27
9x4=36...
And each answer would raise the left side by a factor of 1, and the left side would descrease by a factor of 1.