This was a SUPER fun way to practice missing addends. Give two students a card with a number on it without them looking at it (I just wrote the numbers as the students were coming up so there's no prep which I always LOVE). The class has to add them together and then one of the students standing calls on someone sitting to tell them the total number. The two students have to look at each other and figure out what number they are. So each one knows a part and the whole number and they have to figure out what the other part is. Get ready for lots of giggles!!! You can also put students into groups of three and give them a stack of cards and they can take turns being an addend or the person that adds them together.