Fun with numbers

I'm not a math nut but this one's pretty cool ! Try it out and let me know.

1. Grab a calculator. You won't be able to do this in your head.
2. Key in the first three digits of your phone number (NOT the area code).
3. Multiply by 80
4. Add 1
5. Multiply by 250
6. Add the last four numbers of your phone number
7. Add the last four numbers of your phone number again
8. Subtract 250
9. Divide number by 2

Do you recognize the answer?
It should be your phone number!