Psychic Website Trick is Fun
This is a fun way to exercise those problem solving skills. It requires a little math and a little understanding of how websites work. I showed this to the Junior High and asked them to figure out how to site worked. They were freaked out by it and the teacher was flummoxed, so they really had to work as a group to figure it out. It took some time. I did the same exercise with the teachers to start a prof. dev. workshop, they liked it too.
Need a hint? Pay attention to the final number in each equation.