what are the dimensions of the lightest rectangular box without an open top whose base is a square and whose height is two less than the length of the side of the base?

To find the dimensions of the lightest rectangular box without an open top, we need to understand the given information.

1. The base of the box is a square: Let's assume the side length of the base is 'x'.

2. The height is two less than the length of the side of the base: So the height of the box would be (x - 2).

To find the dimensions of the box, we know that a rectangular box has three dimensions: length, width, and height.

In our case, we have the length and width as x, since the base is a square. We also have the height as (x - 2).

Therefore, the dimensions of the rectangular box without an open top are:
Length: x
Width: x
Height: (x - 2)

Note: Since the question mentions the "lightest" rectangular box, we can assume that it refers to the least amount of material used to construct the box. However, the actual weight of the box cannot be determined unless we know the density and thickness of the material used.