It can take a lot of searching to find good math puzzles to use in the classroom. This set, #1, includes relatively puzzles that don't involve either negative numbers or "order of operations." I like to have one projected on the board as students enter the room and let them debate the answer before class starts. We then start the class with the answer and how it was derived. A fun way to start math class. They could also be used as a "bonus" question on quizzes or homework. The file is in powerpoint and very easy to use.