Assuming you don't intend uponu00a0 stacking the kids on top of each other, you have a 100 square foot (10x10) space to fill. Then, if each kid takes up about 2 square feet, 100/2=50 kids. If you did want to stack them on top of each other, then you would have to assume a height, let's say 5 feet. So, with 10/5=2 you have 2 layers of 50 kids each and 2x50=100 kids.