GeoBoard - Area and Perimeter Introduction
- Walter M. Stroup
Area and Perimeter
Two aspects of geometric figures that are related to size or amount are area and perimeter. Larger objects can often tend to have larger areas AND larger perimeters than smaller objects. It can seem reasonable, then, to want to treat area and perimeter as just two similar ways of comparing the relative size of a figure. After all, if it takes a long time to walk around a building (related to perimeter) it is likely to take a long time to vacuum the floors inside the building (related to area). Area and perimeter, however, are very different aspects of geometric figures. To start with, the block shown below represents one square unit of area. Area is the space or surface that is surrounded by, or included within, the sides of the figure. Each of the sides of the unit square of area show is one unit of length. Perimeter is the total length of the the sides that surround the area. For the block of area shown, why is the perimeter 4?
Things to try ...
ONE BLOCK Drag one letter to a near letter. 0.5 is another name for half. Why is the area half? Looking at diagram, why is perimeter greater than 3? How could we figure out the length of the diagonal side? TARGETING AREA OR PERIMETER Move the blue slider to the right to turn on more dots. Move the letters around. What do you notice about the AREA and PERIMETER values? • Create a figure with an AREA between 6 and 12. Explain the value for the Area. Determine the length of EACH side (you do not need to use a formula). OR • Create a figure with a PERIMETER between 5 and 8. Explain the value for the Area. Determine the length of EACH side (you do not need to use a formula). Related activity GeoBoard - The area & perimeter BLOB https://www.geogebra.org/m/b7682csu