# 7. Understand connections between subcategories of two-dimensional figures (C)

teaches Common Core State Standards CCSS.Math.Content.5.G.B.3 http://corestandards.org/Math/Content/5/G/B/3
teaches Common Core State Standards CCSS.Math.Content.5.G.B.4 http://corestandards.org/Math/Content/5/G/B/4
teaches Common Core State Standards CCSS.Math.Practice.MP3 http://corestandards.org/Math/Practice/MP3

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Lesson objective: Understand how categories and subcategories of two-dimensional figures are connected.

Students bring prior knowledge that shapes in different categories (rhombuses, rectangles, etc.) may share attributes from 3.G.A.1. This prior knowledge is extended to classifying figures in a connected order, or hierarchy, based on properties as students analyze a collection of figures. A conceptual challenge students may encounter is thinking a figure can only belong to one category at a time.

The concept is developed through work with two-dimensional figures and flowcharts, which illustrate the relationship between classifications of different figures.

This work helps students deepen their understanding of number because students explore the concept that attributes of two-dimensional figures are categorized by the number of sides, angles, and parallel/perpendicular lines that make up the plane figure.

Students engage in Mathematical Practice 3 (construct viable arguments and critique the reasoning of others) as they consider the claims of others in regards to the classification of two-dimensional figures, and make judgements on their reasoning based on their understanding of the classification of plane figures

Key vocabulary:

• attribute
• equivalency
• hierarchy
• parallel
• parallelogram
• rhombus

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