There are 28 question cards and 28 answer cards to use to play Concentration/Memory(math center activity) or cards can be folded to show question on the front and answer on the back to play the fun and engaging Kagan game, Quiz Quiz Trade(cooperative learning). The skill being practiced is Missing Addends or Change Unknown. Ex. 34 + ___= 100. Each card has a hundreds chart showing the first number. Students can easily count on to figure the missing number. After demonstrating how to use the hundreds chart to solve the problem, let students play the games for 5 -10 minutes. You will be surprised on how well they will master the skill through Quiz Quiz trade (directions included). My students love this game. Also included are 2 worksheets to use for a quick assessment.