Mathemagic

hope no one ever introduces him to poker

In fact, he didn't train his brain into going through such complicated calculations, there's a theory that says these people "imagine" numbers like forms and they can "visualize" the result of very complex operations and almost immediatly give the proper answer... The brain is one peculiar organ, some are gifted and others, well are average joes.

I would say that's kinda standard
Though, he is a good showman.
Classical calculation test : extracting 13th root of a 100 digit number.
and you can see a lot of those tests about memory and calculation here : http://www.recordholders.org/en/list/memory.html#

yea, that's kinda standard it's like being winner at nl10.

Are you fucking serious?

On March 07 2011 08:58 ondik wrote: yea, that's kinda standard it's like being winner at nl10. Are you fucking serious?

About saying standard, obviously not.
But, I would guess that there are quite a lot of people doing stuff like this. Those kind of calculations require a lot of work, but can be performed by people you would not consider "genius".
As he explained, he uses : (a+b)²=a²+b²+2ab
so number wxyz²=(wx00+yz)=wx²*10000+yz²+2*wx*yz... so you just have to know 2 squares (wx and xy and do some simple calculations).

On March 07 2011 09:46 kingpowa wrote: Show nested quote + On March 07 2011 08:58 ondik wrote: yea, that's kinda standard it's like being winner at nl10. Are you fucking serious? About saying standard, obviously not. But, I would guess that there are quite a lot of people doing stuff like this. Those kind of calculations require a lot of work, but can be performed by people you would not consider "genius". As he explained, he uses : (a+b)²=a²+b²+2ab so number wxyz²=(wx00+yz)=wx²*10000+yz²+2*wx*yz... so you just have to know 2 squares (wx and xy and do some simple calculations).

duh!

what about when he would guess the day of the week they were born based on their birthdate O_O

They actually use this sort of thinking on black people from compton.

On March 07 2011 11:35 Night2o1 wrote: what about when he would guess the day of the week they were born based on their birthdate O_O

I've read about the method for that too a while ago. Can't remember it now though, but it exists and isn't ridiculously taxing.

On March 07 2011 09:46 kingpowa wrote: Show nested quote + On March 07 2011 08:58 ondik wrote: yea, that's kinda standard it's like being winner at nl10. Are you fucking serious? About saying standard, obviously not. But, I would guess that there are quite a lot of people doing stuff like this. Those kind of calculations require a lot of work, but can be performed by people you would not consider "genius". As he explained, he uses : (a+b)²=a²+b²+2ab so number wxyz²=(wx00+yz)=wx²*10000+yz²+2*wx*yz... so you just have to know 2 squares (wx and xy and do some simple calculations).

The guy IS extremely impressive, but he is not unique. People have done far more impressive feats!

Side note:

Squaring numbers ending in 5 then becomes VERY easy
(x+5)^2=x^2+10x+25=x(x+10)+25

where x is a multiple of 10...

so we can say 'the number in the 10s column is x(x+1)'

45^2=2025.....(4x5 and 25 on the end)
105^2=11025 (10x11 and 25 on the end)

There are occasionally spots where we can use the difference of 2 squares identity... (x+a)(x-a)=x^2-a^2

On March 07 2011 12:10 Oly wrote: Show nested quote + On March 07 2011 11:35 Night2o1 wrote: what about when he would guess the day of the week they were born based on their birthdate O_O I've read about the method for that too a while ago. Can't remember it now though, but it exists and isn't ridiculously taxing.

I guess that you can use congruence on all levels (year, month, day...)

edit : http://en.wikipedia.org/wiki/Calculating_the_day_of_the_week (congruences)