The fortune teller knows his last name _ Does the fortune teller know his name?

Why can the fortune teller on the street know my last name? Scientific explanation. . Thank you. . Thank you for your questions.

Fortune tellers on the street can know my last name. To put it bluntly, it is a math game.

Specifically, it is to write the common surnames in groups on several pieces of paper in advance, and then let you tell which pieces of paper have your surnames (different papers have different marks), and then you can get the correct results by simple calculation.