Lesson 4

Area of Composite Shapes

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SWBAT find the area of composite shapes by finding the sum of the areas of its component shapes

Big Idea

Students build on the previous lesson to find the area of composite shapes.


10 minutes

I will hold up a triangle and a rectangle.  I will put them together to make one shape.  I will then ask the essential question:  How can you determine the area of a composite shape?  When students mention the various formulas that could be used to find the area they are modeling with mathematics (MP4).  I will ask these questions as THINK-PAIR-SHARE questions.    I want the students to generate steps to solving area problems before I present them with a list.  We will finalize the list of steps and I will model 1-2 problems for the students.  A grid is provided but only as a tie-in to the previous lesson.

Guided Practice

10 minutes

Students work in pairs to solve the problems.  Many of these problems are similar or identical to problems from the previous day.  The only difference is that students are expected to make all subdivisions without using graph paper.  Being able to make subdivisions to identify composite shapes goes with MP7.  I will make sure students are clearly labeling their work – especially the formulas for the individual shapes (MP6).

Independent Practice

15 minutes

 If students are able to perform these without difficulty we will move directly into independent work.  I will then assist students who continued to struggle with the guided practice.  For the first few problems, I’ll be on the lookout for students who incorrectly treat the shape as 1 large rectangle.  I expect a few students will correctly solve problems 1 & 4 using a subtraction method.  That is okay.  If it occurs I will present it as another way when we go over solutions.   

Lesson Summary + Exit Ticket + Homework

10 minutes

I will look for two different examples of correct solutions for each problem.  We will discuss them briefly.  I will repeat the essential question and ask or cold call for student responses.  Students will then take the exit ticket solving problems similar to the examples.