Everyone in the class is given a card with a statement such as "I am 7, who is a+b+c?". The person who is the answer speaks up next by reading their own card.
The game finishes when everyone has read out their card.
This could be an exercise in making no errors or it could be a speed test.
Alternatively, each person could be given a card and asked to get into a circle standing next to the people who hold the next cards in the sequence.