A geometric shape is characterized by:
- Its outline : closed line that delimits the shape of the figure (the boundary).
- Its surface area: the space contained within the boundary
Two main measurements are associated with figures:
- The perimeter measures the length of the contour line. This measure is expressed in meters (m) or one of its derived units of measurements (mm, cm, km, ...), or in non conventional unit like the number of segments.
- The area measures the surface area of the figure. This measure is expressed in square meters (m2) or any of its derived unit (cm2, mm2, km2, …), or in non conventional unit like the number of tiles.
In ancient times, the area and perimeter measures were strategic. The allotment of lands were done in accordance with some measurements and it could disadvantage naif peasants. The perimeter of a surface was counted in steps but how could they measure the area to cultivate?
There is no direct link between the area and the perimeter of a figure. Two different figures can have the same perimeter and have different areas or have the same area and different perimeters.
The perimeter measures a length, it is a one dimension measure. Before the meter was imposed as the universal measure unit in 1795, other units of length were used like a step, a stadion, a…