Answer: Independent
Explanation:
The independent variable in an experiment is the one that is not dependent on the other variable being measured. It is the variable that is manipulated such that the groups being experimented on get varying amounts of it so that their effect on dependent variable can be seen.
In this scenario, the mathematical problem-solving ability is being investigated to see if it depends on the number of Jumping jacks done and so the 2 groups were given a different number of jumps to do. Jumping jacks are therefore the independent variable.