Fun Math Puzzle

I found this puzzle in the July/August 2008 Family Fun magazine. Calder loved doing it last year. Be prepared to do every friend and family member's phone number you know. Over and over and over again!

1. Multiply the first three digits of your phone number (not your area code) by 80.
2. Add 1.
3. Multiply by 250.
4. Add the number formed by the last four digits of your phone number.
5. Add that four-digit number again.
6. Subtract 250.
7. Divide by 2.

The final answer is...your phone number!