The Flash Mind Reader - How does it work?

There's always one guy

There's always one guy that spoils things for the rest of us. That's me.

The answer will always be a multiple of 9. All the multiples of 9 in the chart correspond to the same symbol --the same one that appears in the crystal ball.
 
use 99 as your number
 
WhaWhaWha said:
The answer will always be a multiple of 9.
A little arithmetic proof:

Look at a two digit number, "ab."
What it represents is a x 10 + b.
...which can be written as a(9 + 1) + b,
...which is the same as 9a + (a + b).
When you pick a two digit number and subtract from it the sum of the two digits, that would look like this:
9a + (a + b)
- (a + b)
______________
= 9a

What that means is that taking any two digit number and subtracting the sum of the digits gives you a multiple of 9. The "mind reader" is programmed to just show the current "multiple of nines" symbol (which for any trial is the same for each multiple of nine).