An important part of educating young people is teaching them how to solve problems and 'think outside the square'. I've created a page on my blog which is a collection of the problems I've seen used in classrooms or around the traps as it were. Feel free to use them in your own classrooms and provide answers to the ones I haven't worked out yet! The link is in the side bar (Problems for the thinking classroom) or go to http://eaholliday.squarespace.com/problems-for-the-thinking-clas/ . Cheers!