Amazing Pre-shool Maths Formula

Feeling dull on the black and white accounting system, worsen by Monday blue effects and a hazy morning? Try this funny maths...reproduce any given 7-digits code (e.g. last seven digits of a cellphone number, ICQ number, etc), after applying that number with a series of simple pre-school calculations:

1. Enter first 3 digits of the 7-digit code to your normal calculator.
2. Multiply the number by 80
3. Add 1 to the previous result
4. Multiply the result from previous step by 250
5. Plus the result with the last 4 digits of the number
6. Plus last 4 digits of number once again to the previous step result
7. Minus it with 250
8. Divide it by 2
9. Bingo! That is the original 7-digits code.