A line.
it only has one face and has no edges or vertexes and also is circular
Plane.
If you are a cube, one of the sides is called a face. Same with a cone, the flat part is a face.
-1
It would not fit unless you sliced off 2 of its dimensions.
They are flat surface figures like squares and circles. 3D figures have length, width, and height like cubes and spheres.
It is a 7 sided heptagon whose 7 interior angles add up to 900 degrees
A figure of speech
A pyramid is a solid figure with one vertix.
Rounded to one significant figure it becomes 20
A plane figure is one that is entirely in one plane. One way to think of that is it can be made to lie flat - no ups or downs. A closed figure is one where you can go around the outside of the figure and return to your starting point - without jumping. If you take any two points - one inside the figure and one outside, then you cannot draw a curve from one to the other without crossing the boundary of the figure.
1000 is written with one significant figure, with only the 1 being a significant figure.