Final answer:
To find the number of quarter horses in the stalls, subtract the number of ponies from the total number of horses. There were 550 quarter horses in the stalls on Tuesday.
Step-by-step explanation:
To find the number of quarter horses in the stalls, we first need to determine the total number of horses in the barn. Given that the barn has stalls for 1000 horses and it was 75% full, we can calculate that there were 750 horses in the barn on Tuesday.
We are then told that 40% of the stalls are for ponies, and there were 200 ponies. To find the number of quarter horses, we subtract the number of ponies from the total number of horses: 750 - 200 = 550.
Therefore, there were 550 quarter horses in the stalls on Tuesday.