Students work in paris to answer questions. When they have an answer they bring it to be checked. If it's right they get the next questions if it&'s wrong they go back and check it. There is a page of questions to print and cut into strips. The questions get harder so that as they get nearer to the end groups start catching up. Usually takes 30 - 45 minutes to get a winner or can be who can get furthest in the time allowed. I find it helpful to have the slips on the 1st page for answers so that they keep their working out seperate and answers can be checked quickly but paper works fine.