Math trick

[swing]

Got this in an email, so many of you may have already seen it.

1. Grab a calculator.
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 4 digits of your phone number.
7. Add the last 4 digits of your phone number again.
8. Subtract 250.
9. Divide number by 2.

Do you recognize the answer?