Fun fact, about a hundred years ago, some pseudo-mediums would use a similar kind of math trick to "guess" the number of deceased brother and sisters of someone coming to see them in order to do a Seance.
Morality aside, discovering that highly surprised me because I always thought that those techniques were transparent to all people. But I guess math literacy in the US wasn't always great...
Morality aside, discovering that highly surprised me because I always thought that those techniques were transparent to all people. But I guess math literacy in the US wasn't always great...