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

1. Grab a calculator. (You won't be able to do this one in your head)
2. Key in the first six digits of your mobile number
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?