Discovering Area Relationships of Polygons
Students discover the area formulas for triangles, parallelograms, and trapezoids. They apply formulas to find areas of irregular shapes.
This can be done as a whole class or with partners. Project (or provide copies) of the "Cork Costs" graphic. Ask students: What do you notice? What do you wonder?
Lesson 1 of 4
Students develop the area of triangles formula using the area of rectangles and by comparing triangles with equal bases and heights.
Lesson 2 of 4
Students use prior knowledge of the area formula for rectangles and triangles to discover the formula for the area of parallelograms.
Lesson 3 of 4
Students explore several strategies for calculating the area of a trapezoid while discovering the area formula for trapezoids.
Lesson 4 of 4
Students will estimate the area of irregular shapes and use a process of decomposition to calculate the areas of irregular polygons.