Flash Mind Reader - explained

Lot’s of people have been asking me how that Flash Mind Reader thing I featured on my site last week works. So here’s an explanation I found on the web. I only wish I could find out where I got this so I could give the person credit.

“..it works the same way as most number tricks do: math + sleight of hand + misdirection + design. First, the math part. The instructions say to choose any two digit number, add the digits together, then subtract the total from your original number. When you do that, the result will be a multiple of 9, NO MATTER WHICH NUMBER YOU CHOOSE. It even works for bigger numbers, not just two digits. If you’re skeptical, pick a few numbers and try it yourself. Why does that work? I dunno, number theory or something? But it’s guaranteed, and it’s the first key to the trick.

Next comes the sleight of hand. Back at the Mind Reader, take a look at the first four multiples of 9, starting with 9, then 18, 27, and 36. They all have the same symbol. You probably figured that would happen, now that you know about the math part. Now click the crystal ball. Check the symbols for 9, 18, 27, and 36 again. HEY, THEY CHANGED! It’s still the same for all of them, but it’s a different symbol. Did it occur to you that the symbols were changing every time you guessed? Most people don’t imagine that possibility. It’s sneaky! In this trick, it’s the second key. If the symbols didn’t change every time, the trick would quickly lose its luster.

The third part is a bit of misdirection. Check out the symbols for the two highest multiples of 9: 99 and 90. They’re not the same as all the other 9s. That’s because they will never be your numbers in this trick. The highest original number you can choose is 99. 9 + 9 = 18, and 99 - 18 = 81. Your number will never be higher than 81, so having different symbols for 90 and 99 is a red herring. Another clever touch is listing the numbers backwards, from highest to lowest, so if you suspect something about powers of 9, you’ll probably start by looking at 99 and 90. When they have different symbols, you’ll be thrown off the trail. Nice.

The final reason why Flash Mind Reader works so well is its wonderful design. It’s not called “Flash Trick Based On Math, Etc.”. It’s hidden behind cool, magical stuff: a crystal ball, mystical symbols, groovy sounds, and no explanations. It’s a great magic trick for the web. Bravo, Andy Naughton!”