Activating Strategy

What questions could you ask?

• What have we learned about in previous lessons that might relate to the image?

• What do you notice about the overall shape formed by the playground tiles?

• How can I decompose the area of the playground into smaller shapes?

The playground shape is a composite rectangle, which is made up of two or more rectangles. When I see a composite rectangle and am asked to find its area, I think about how I can decompose it into two or more smaller squares or rectangles because I can find the area of rectangles and squares by multiplying the length and width.

To find the perimeter of a composite figure, I need to add all the side lengths. The formula 2(length + width) is used to find the perimeter of a rectangle, but this formula does not work for a composite rectangle.

I also noticed that I am missing one of the side dimensions, so I will first need to solve the missing dimension to find the area and the perimeter.

I will use the dimensions given in the diagram to help me create the diagram with color tiles. I can think about decomposing this composite rectangle into two smaller rectangles.

Next, I see that the left vertical line's dimension is 5 meters, and I have only built a side with a dimension of 3 meters, so I need to add two more meters to that side. I also see that the horizontal dimension at the bottom of the diagram is 10 meters long. This means I need to add two more rows of 10 to my color tile diagram.

Guided Practice

Mathematicians, it is your turn to try!

Deka’s school plans to build a new sandbox in the new playground. The diagram below shows the outline of the sandbox. How can we determine its area? What is its perimeter?

When working in your collaborative groups, please remember that to find the area of a composite rectangle, you must decompose the composite rectangle into two or more smaller rectangles or squares so you can use the area formula (Area = length + width). 

Sometimes, you need to use your knowledge of rectangle and square attributes to help you solve for unlabeled side lengths. To find the perimeter, add ALL of the side lengths.

In your small groups:

1. FRECKLE - Complete THREE Freckle Assignments each week. DUE FRIDAY. Your HIGHEST score in Targeted Practice is your weekly math grade - Click HERE for Freckle website

• GRADED Targeted Practice - Current skill (5 questions; Score Goal=80% or higher)

• Fact Practice - Multiplication Fact Practice

• Adaptive Practice - At YOUR level

2. iREADY Math - Complete 30 minutes at your level each week