I find it very interesting hehehe. My friends are starstrukk, lol. Here's h0w:
<Ask s0meb0dy to think of a number and keep it a secret.
<Then ask that pers0n to d0uble the secret number and then multiply by 5.
<Finally, ask f0r the total.
<Whatever the total is, kn0ck off the last digit and y0u will have the secret n0. the pers0n mentally chose at the start.
