how do things like these work?

[mayanks_098]

see this,a very common trick,this is just one of the many variants of the trick.
how do these tricks work?
i mean whats the logic behind?
and how do you make such a trick?
and why does no one gets an incorrect answer?




*www.mysticalball.com/

 

[piyush gupta]

Very very old one

 

[ilugd]

pretty simple actually.
let us say you have a number xy where xy is a two digit number and x and y are the digits. (note xy is not multiplication)
when you say xy - (x+y) = xy - x -y = x0 - x

get that? actually you are just rounding it off to the lesser multiple of ten.
So now we have a multiple of ten.
x0 - x = x (10 -1) = 9x
the result is always a multiple of 9
And guess what is the symbol for all multiples of nine? Surprise!!

it gets ****ed up if you go for 3 digit numbers. And two digit number never gives a result above 81 so don't worry about the symbols for 90 and 99

 

[The_Devil_Himself]

^^+1
Simple let the no. you select is z with x at tens place and y at units place.So z=10x+y.Ok now it tells you to subtract x+y from it i.e. 10x+y-[x+y]=9x.SO the answer is always a multiple of 9 no matter what no. you select.As you can see all the symbols are same for the multiples of 9.


They also change that symbol on the multiples of 9 so that you don't become suspicious.

 

[mayanks_098]

thanks.
but what about those illusions in which you see dots appearing/disappearing?hope you have seen something like that

 

[navjotjsingh]

example?

 

[The_Devil_Himself]

thanks.
but what about those illusions in which you see dots appearing/disappearing?hope you have seen something like that

Optical illusion dude.