The key to solving this question is to know that a square is also by definition a rectangle. The minimum perimeter of a rectangle must be when the case for a rectangle is a square, so both sides are of the same size.
Therefore, if we know that the area of a rectangle is
A = l x h
But if these two sides are the same (because this is the case where the rectangle is a square), we have:
Suppose h = l.
Then
A = h x h
A = h^2
sqrt(A) = h
Therefore
h = sqrt(A)
A = 625ft^2
h = sqrt(625ft^2)
h = 25ft
Then, the perimeter is
P = 25ft + 25ft + 25ft + 25ft or
P = 4 * 25ft = 100ft
So, the minimum perimeter is 100ft.