Here is a math trick so unbelievable that it will stump you.

Grab a calculator. (you won't be able to do this one in your Head)

1. Key in the first x* digits of your phone number (NOT the Area code)

* [if ur mobile Number has 7 digits, then x = 7-4 digits]

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 ?? :?: :?: :?: :?: