Answer:
3-D shapes and 2-D shapes are similar because they have angles and dimensions. 3-D shapes and 2-D shapes are different because one is flat, while the other is not. Considering that a triangle has 3 angles, 3 sides, and a square has 4 angles and 4 sides, they are interesting shapes. One interesting thing about a triangle is its interior angles are always 180. Another fact is about squares. Squares' angles always intersect at 90 degrees, and it usually has a larger area than most quadrilaterals.
Hope this helps.