Process

**Assignment**
 * Great job 4pts [[image:hearts_and_arrow.gif]]**

Check the following web page in which you have a magic trick. []

Follow these steps: 1. Read the instructions, cut them and paste them ** to your wiki **. 2.Underline the words that are time markers. 3. Play and try to explain why the magic trick worked. 4. Check the explanation below the trick. Was it the one you were thinking of? Explain.

Answers :

=An Arithmetic Magic Trick =

Think of a 2-digit integer. Subtract from the number the sum of its digits and find the result in the table below. Note that each cell of the table contains a number and a geometric shape. Concentrate hard on the shape that shares a cell with the result of your calculations. __When__ ready, press the "Check it!" button ...

3) I looked at it for a long time and I have no clue how this works.

 Let the number you thought about be 10a + b. Subtracting the digits gives


 * || (10a + b) - (a + b) = 9a ||

which is __always__ a multiple of nine. If you look carefully at the table, you will not fail to notice that all multiples of 9 are in cells with the same shape. This is the shape you are to notice and concentrate on.

(Without the computer, this property of the decimal system can be used as a similar one is employed in the [|Math Telepathy trick]: __after__ you calculate the result and tell me one of the digits, I magically produce the other digit of that number.

4) I read the explanation and I was amazed, I can't COULDN'T believe something so amazing can be done with math.