First, each student has invented four easy additions and we have written them on white popsicle sticks.
Second, each student has invented a bit more difficult additions and we have written them on green popsicle sticks.
Them, we played MIKADO: you pick up a stick and say the result. If the result is correct, you keep the stick. At the end of the game, you get two points for each green stick and one point for each white stick you have.
When we do not agree on the result, we check it using the calculator.