When deciding the probability of an event through experimentation, how many trials are enough? 10? 1,000? 1,000,000??? This activity is a cooperative grouping activity that focuses on just that. The pre-lesson set up reels the students in. The activity engages them. The manipulative materials involve them. An Excel extension is also available to combine the results of multiple groups. Through this activity, students really see how more trials leads to a better understanding of the true pr