Brain Teasers for Brainy Students

My adult students love quizzes. I usually divide the class into two teams .The worksheet has 14 brain teasers, so each team has seven. Each team has a sheet with answers to the brain teasers for the other team. I appoint a chairperson and all answers have to be approved by him or her. No calling out! The teams get a point for every correct answer. The team with the most points usually gets a treat which they always share with the "losers". I feel quizzes test both their vocabulary and use of English.They are always fun and can prove quite interesting  in regard to hierarchies in classes, I usually appoint the quieter students as chairpersons. In conversation classes they are expected to explain their answers.