I've never done this before, but if it is balls per square foot, then i can figure it out. It is 2 balls per square foot
Step-by-step explanation:
If the gym is 100 ft by 60 ft, it will be 6,000 square ft. Since there are 12,000 balls, you divide it by 6,000 (12,000/6,000), which is 2, so it would be 2 balls per square foot
Let the number of years after 2001 be x, then 1280000 + 19500x = 1700000 19500x = 1700000 - 1280000 = 420,000 x = 420000/19500 = 22 years. x = 22 years.