Tonight, Partner and I saw an off-Broadway show of a guy doing fast math in his head. He calls himself a “math-e-magician.”
This performer does a great job of playing things off. One of his acts is to to guess the missing digit of the answer to an incredibly long multiplication problem. Starting with a 4 digit number from a previous trick, each audience member uses their phone calculator to multiply by a new 5 digit number that they don’t say out loud, and then they read all but one digit aloud. Give the digits in any order — he can still figure out what’s missing.
Magicians never reveal their secrets, but, for a math-e-magician, the reveal is part of the show. The trick is that he selected a multiple of 9 as the starting number. Therefore, the sum of the digits will always be a multiple of 9. So if The sum is 68? The next multiple of 9 is 72, so the answer is 4. The sum of the digits given is 34? The missing digit is 2 (34+2=36, 36/9=0). The sum of the digits is 45? Well, the answer could be 0, or it could be 9.
This is what separates the magicians from the math-e-magicians. And math-e-magicians reveal their secrets.
He cold-reads. He will say, “I’m going to read your mind… I’m getting a lot of nothing. It’s not zero, is it?” And if the audience member says, “That’s right!”, we’re good.
But if the audience member replies otherwise, he can say, “Try thinking harder… It’s nine!”, just playing it off like it was part of the act.
Cold-reading psychics do this as well, where they might see a woman crying and say, “It’s not your husband, is it?” and if the response is yes, they say, “Yeah, I thought so.” But if the answer is no, they say, “Yes, I didn’t think so.”
Either way, the phrasing gives you that particular out.
My favorite and least-favorite part of the show was when an audience member kid said that he could do 75 digits of pi, and then he could not accurately do 75 digits of pi. The performer did a great job of making the kid not realize he was flailing. The performer had said, “We’re going to do 60 digits of pi, and then maybe continue onwards.” And since the kid was flailing, the performer cut him off.
Partner’s favorite part was when he asked a little girl for her birthday, and did a whole act with the numbers in it. He then asked for someone else’s birthday, and the girl’s sister volunteered. But the sister was quick to point out that she’s not just a sister: she’s a twin. The performer chuckled and used the birthday anyway.
This particular performer used to create magic squares to entertain himself. Now he performs math-e-magic in an Off-Broadway show.
Starting early sure helps.
Julian Wise 