How many1 ft square items fit in a 4000 square foot space?

Answer 1

It can depend on the shapes.

Suppose each item is 1 ft x 1 ft so that its area is 1 sq ft,

and

suppose the space is 0.5 ft x 8000 ft so that its area is 4000 sq ft.

Not a single item will fit in the space.

Conversely, if the items are very thin and long and the space is nearly square, you may find that no items fit.

But leaving aside these two extreme situations, 4000 items may fit. That is certainly the maximum number of items.