The wonder of Maths‏

Dear Friends,
The wonder of Maths.. How do these people know how to work this out?

1) Key-in the first 3 digit of your handphone number (not the 01x number) into the calculator
2) multiply by 80
3) add 1
4) multiply by 250
5) plus last four digit of phone number
6) plus last four digit of phone number again
7) minus 250
8) divide by 2

Is it your handphone number???? AMAZING!!!!!

Cheers!