Put students in small groups of 2 or 3. Make multiple copies of the rational numbers problems. Give each group the same problems face down and have them write their names on the back. When you tell them to GO, they turn it over to solve the problem. Once solved, they bring it to you, and you tell them if they are correct. If they are, they put the paper in a box, hat, etc and receive the next problem. If they are incorrect, they go back and try to solve again. They don't get the next problem until they are correct. At the end of the time allotted, you mix up the box with the papers in it and pull out the winning team. They receive a prize of your choice.