There’s an old magic number guessing trick, where the magician shows asks an audience member to think of a number from 1 to 100, then shows them seven cards. Each card has about 50 different numbers written on it.
The subject says whether their secret number is on each card. At the end, the magician pronounces “Your secret number is…. 54!” (or whatever it was).
I got an email about a month ago, from someone who had such a set of cards, but had lost one! They asked – had I heard of the trick, and did I have something like it on my site? The answers then were “yes” and “no”, but now they’re both “yes”.
At http://www.dr-mikes-math-games-for-kids.com/magic-number-cards.html you’ll find everything you need to perform this old, traditional magic number guessing trick, including a set of cards you can download and print, and full instructions on how to use them. Ok, you also need an audience to amaze – you’ll need to provide this yourself.
I’ve also invented a few variations on the trick. The page also has…
* A different set of 7 cards where the trick is easier for the magician, and more obscure for the subject…
* A set of 10 cards for discerning numbers up to 1000…
* A variation of the trick allowing the magician to discover numbers up to 100 with only 5 cards instead of 7.
There’s also a home video movie clip showing my son performing the trick. If he looks sleepy, it’s because I’d just woken him up. It was the only time we could find when his younger brother wouldn’t interrupt!
So, once the Christmas toys have been tossed aside, and it’s too cold or wet to play outside, try teaching your kids this magic trick – see if you can get them ready to baffle their friends when the new school year begins… 🙂
Michael Hartley
Dr Mike’s Math Games for Kids