One question, two teams, fastest finger wins. The same mental maths question appears in the middle and both teams see the same four answers. First to tap the right one takes the point, but tap a wrong one and you're locked out while the other team thinks. First to 10 points wins the faceoff.
Built for an interactive whiteboard or a shared tablet: one player (or team captain) stands at each side. The lock-out rule is the clever bit, as it punishes wild guessing. The winning strategy is to be fast AND sure, which is exactly the balance a timed maths paper demands. Mixed addition, subtraction, tables and division keep everyone on their toes.