# How does this work?

Hi
I’m new to these boards. Can someone please explain how Flash Mind Reader works?
Alma xx

It works because the number you end up with is always a multiple of 9, and in the chart all the multiples of 9 (9, 18, 27, etc.) have the same symbol.

Now why do you always end up with a multiple of 9? It has to do with a well-known property of numbers: If you add up all the digits in a number, and add up all the digits in the sum, continuing until you are left with one digit, then that one digit is the remainder of the original number when you divide by 9. (If the one remaining digit IS 9, then the orginal number was divisible by 9.)

So if you subtract that number from the original, you are subtracting the remainder from the original, which must leave a number divisible by 9.

Ed

Here’s how the multiple of nine result was explained to me, as basically an algebra equation:

(I hope typo mna doesn’t mind me quoting him from another board. Eh, what do I care? What’s he going to sue me for? \$12.50 in returnable bottles?)

“The instructions are to pick a number, add the digits and subtract from the original number. If a is the tens place and b is the ones place, the number is (a times 10) + b. When you add the digits together, you get a + b. Subtracting that from the original number gives the equation (a times 10) + b - (a + b), which equals (a times 9) + b - b, or a times 9. Which, as was pointed out, is a multiple of nine, so it always matches the symbols next to the multiples of nine.”