Math problem

Here's one that is fun. We don't know
who actually had enough time to figure
this out......way too much time on their
hands....
get a calculator, key in the first three
numbers of your phone number (not area code).
multiply by 80
add one
multiply by 250
add the last four numbers of your phone #

add the last four numbers of your phone # again
minus 250
divided by two......

What is the answer? Yes, it works.....OH MY!