Following is how you do it
Grab a calculator. (you won’t be able to do this one in your Head)
1. Key in the first four digits of your landline phone number (NOT the
Area code ...)
2. Multiply by 80
3. Add 1
4. Multiply by 250
5. Add to this the last 4 digits of your phone number
6. Add to this the last 4 digits of your phone number again.
7. Subtract 250
8. Divide number by 2
Do you recognize the answer ??
A pretty useless thing but some one have surely put in a lot of effort to some up with this cool trick