Have students work in partners productively and accurately with this engaging self-checking tool. Students are paired up together and each is assigned the problems associated with "PARTNER A" or "PARTNER B". Partner A works through the problem in that column and Partner B works through a different problem that is in that column. If both students do their problems correctly, they will arrive at the same answer! My students have had a great deal of success with this activity and were able to figure out their mistakes. It will also give you the piece of mind that students will know quickly whether or not they have done the problem correctly.