Via (used with permission)

Blow up a multi-colored beach ball, then using a sharpie, draw an “equator” on the ball, then number each section from 1 to 12. Toss the ball to different family members and call out the operation to perform (e.g. addition / subtraction / multiplication / division / identification). The catcher must call out the problem based on the numbers indicated by his/her thumbs and the solution as quickly as possible, then toss to the next person. If the answer is wrong and the ball has already been tossed, that person is OUT. Whomever is the “last one standing” is the winner.

Thumb Ball