Thanks to KJ: A Quick Little Problem

This is really worth doing and it's a quick little problem if you follow the instructions.
1. Grab a calculator---not an adding machine (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 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?