# 3.8 - Perimeter and Area

The student will

a)  estimate and measure the distance around a polygon in order to determine its perimeter using U.S. Customary and metric units; and

b)  estimate and count the number of square units needed to cover a given surface in order to determine its area.

### BIG IDEAS

• So that I can measure my back yard to find out how much fencing is needed to close it in

• So that I can determine how much paint is needed to paint my bedroom

### UNDERSTANDING THE STANDARD

• A polygon is a closed plane figure composed of at least three line segments that do not cross.  A plane figure is any closed, two-dimensional shape.
• Perimeter is the path or distance around any plane figure.
• Area is the number of iterations of a two-dimensional unit needed to cover a surface.  The two-dimensional unit is usually a square, but it could also be another shape such as a rectangle or an equilateral triangle.
• The unit of measure used to find the perimeter or area is stated along with the numerical value when expressing the perimeter or area of a figure (e.g., the perimeter of the book cover is 38 inches and the area of the book cover is 90 square inches).
• Opportunities to explore the concepts of perimeter and area should involve hands-on experiences (e.g., placing toothpicks (units) around a polygon and counting the number of toothpicks to determine its perimeter and filling or covering a polygon with tiles (square units) and counting the tiles to determine its area).

### ESSENTIALS

The student will use problem solving, mathematical communication, mathematical reasoning, connections, and representations to

• Estimate and use U.S. Customary and metric units to measure the distance around a polygon with no more than six sides to determine the perimeter. (a)
• Determine the area of a given surface by estimating and then counting the number of square units needed to cover the surface. (b)

### KEY VOCABULARY

Updated: Aug 22, 2018