Unit 2, Lesson 10
Solve Area Problems
Grade 3
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The purpose of this Number Talk is to elicit strategies and understandings students have for multiplying within 100. These understandings help students develop fluency and will be helpful later in this lesson when students multiply side lengths to find area. While recording students’ thinking, consider using equal groups or arrays, as in the images in the Warm-up of the previous lesson.
Find the value of each expression mentally.
None
The purpose of this activity is for students to solve a real-world problem involving area. The activity includes a rectangle in which the side lengths are labeled. When students solve problems with multiple solutions and have to choose and justify a solution, they make sense of problems and persevere in solving them (MP1). In their small groups and in the class discussion, students have an opportunity to explain and defend their choices (MP3).
Noah is painting a wall in a community garden. The wall is shaped like a rectangle. A diagram of the wall is shown here.
Paint is sold in 3 different sizes:
What should Noah buy? Explain your reasoning.
MLR6 Three Reads
To Copy (from Blackline Masters)
Centimeter Grid Paper - Standard
The purpose of this activity is for students to solve an area problem that involves unknown side lengths. The problem has multiple solutions, with the area of the garden between 20 square feet and 30 square feet. The Launch serves to familiarize students with the ideas involved in designing a garden before they solve the problem.
When students share with other groups and describe what others did that was different, they are making and understanding mathematical arguments (MP3).
This activity uses MLR6 Three Reads. Advances: reading, listening, representing.
MLR6 Three Reads
Elena is planning to build a raised garden bed for the community garden. The garden bed will be rectangular. One side must be 3 feet long. To fit all her plants, Elena needs the bed to cover at least 20 square feet. She has enough soil for a garden bed that covers 30 square feet.
What are some possible sizes for the garden bed?
Create a poster to show your thinking. Organize your poster so it can be followed by others.
As you look at the posters with your group:
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