Two Dimensional means that there are two dimensions.
Because they are dimesional figures either way!
It is a line.
A three dimensional shape is where you have height, width, and length where as in a two dimensional shape you only have height and length
a dodecahedron
In mathematics, they are usually refered to as Solids.
A rectangular solid is 3-dimensional, but I'm assuming you mean a 2-dimensional representation of a rectangular solid, which is called a net. Do a search for the following: "net rectangular prism" and you will see a drawing of it.
With great difficulty. A volume is a cubic - or 3-dimensional - measure. So a volume square is a hyper-volume in 6-dimesional space.
It depends. Different objects require different formulas. For a basic cube, it is width times length times height
Any 2-dimensional shape can be folded to form a 3-d shape. For example, any work of origami.
1.9 cm cannot describe a mass. A mass must be 3-dimesional object, 1.9 cm givs the measure of only 1-dimension.
Yes, as long as the equilateral triangles are all of the same dimensions. One can be he base while the other three will have one edge on the base and he other two connecting to another triangle with the three standing up triangles meeting at one point.
like you can draw a three dimesional repesentation of a cube on a shhet of paper so we can "draw" a three dimesional representaion of the fourth dimension .It would be a cube inside a cube with all of the corners joined by a line from exteranl surface of the inner cube to the inner corner of the external cube. This in affect is a shadow of the fourth dimesion. See "Flatland" for explaination of how 2D would try to describe 3D..