This is a great trick to play on your friends. You can even design your own version of Mind Reader. It isall based on a bit of algebra, but it's really fun!
Try it yourself first using this online demonstration. Read the explanation at the end and then try it on your friends!
How many different versions can you think of for this trick?
Does it only work for whole numbers between 1 and 10? Why or why not?
Does it work for negative numbers?