Calculating the Area of Rectilinear Figures Unit of Study 15: Understand Area Global Concept Guide: 3 of 3

Content Development  Make sure to provide real world applications when working with area to make problems relevant to students and deepen their understanding.  Composing and decomposing complex shapes are valuable activities. They give students the opportunity to connect what they know about the properties of shapes with what they are learning about area.  Students can decompose a shape into smaller shapes and add the area of the smaller shapes to find the area of the larger shape (Figure 1) or they can fill in the missing piece to find the area of the whole shape and then subtract the area of the missing piece from it (Figure 2). Figure 1: Figure 2:

Day 1  The focus of day 1 is using the attributes of a shape to find its area.  Sample Task: Students can work with rectilinear figures on grids and partition them into different sized rectangles.  Note: There is not one way to decompose either of these shapes. They can both be decomposed in many different ways.

Day 2  The focus of day 2 is determining if the formula for area works for rectilinear figures.  On day 2, students should be provided with figures that are not on grids. This will allow them to rely on the properties of shapes and their knowledge of the formula to calculate area.  Sample Task:

Enrich/Reteach/Intervention  Reteach:  The intervention listed within the lesson “Find the Areas of Complex Figures 1” located on the GCG under Lesson Ideas can be utilized. This allows the students to mark off each rectangle by coloring in or using different color rubber bands (on Geoboards) to find the area of the larger rectilinear figure.  Enrich:  You can utilize the extension activity on the lesson “What is the area?” located on the GCG under Lesson Ideas. Students will find the area of the shapes after they find the correct length or width of the shapes.