Cool math trick

[Lisa]

Here is a math trick that looks really neat.
Some people would say who ever came up with this should running the country, personally I think they're wasting too much time coming up with neat math tricks

1. Grab a calculator. (you won't be able to do this one 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?