Lesson 14 | Shapes and Angles | 4th Grade Mathematics

Objective

Analyze and classify triangles based on side length, angle measure, or both.

Common Core Standards

Core Standards

The core standards covered in this lesson

4.G.A.1 — Draw points, lines, line segments, rays, angles (right, acute, obtuse), and perpendicular and parallel lines. Identify these in two-dimensional figures.

Geometry

4.G.A.1 — Draw points, lines, line segments, rays, angles (right, acute, obtuse), and perpendicular and parallel lines. Identify these in two-dimensional figures.
4.G.A.2 — Classify two-dimensional figures based on the presence or absence of parallel or perpendicular lines, or the presence or absence of angles of a specified size. Recognize right triangles as a category, and identify right triangles.

Geometry

4.G.A.2 — Classify two-dimensional figures based on the presence or absence of parallel or perpendicular lines, or the presence or absence of angles of a specified size. Recognize right triangles as a category, and identify right triangles.

Foundational Standards

The foundational standards covered in this lesson

3.G.A.1

Geometry

3.G.A.1 — Understand that shapes in different categories (e.g., rhombuses, rectangles, and others) may share attributes (e.g., having four sides), and that the shared attributes can define a larger category (e.g., quadrilaterals). Recognize rhombuses, rectangles, and squares as examples of quadrilaterals, and draw examples of quadrilaterals that do not belong to any of these subcategories.

Criteria for Success

The essential concepts students need to demonstrate or understand to achieve the lesson objective

Classify triangles according to their side length, and understand each type as equilateral (has all three sides of equal length), isosceles (has two sides of equal length), and scalene (has no sides of equal length) (MP.2, MP.5).
Classify triangles according to their angle measure and understand each type as acute (has all three angles that are acute), right (has a right angle), and obtuse (has an obtuse angle) (MP.2, MP.5).

Tips for Teachers

Suggestions for teachers to help them teach this lesson

Lesson Materials

Template: Triangles (1 per student or small group) — This material should be cut into pieces before the lesson.
180° Protractor (1 per student)
Ruler (1 per student) — This can be any tool used to verify equal lengths, e.g., the edge of a piece of paper, etc.

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Anchor Tasks

Tasks designed to teach criteria for success of the lesson, and guidance to help draw out student understanding

25-30 minutes

Problem 1

a. Sort the shapes (cut out from Template: Triangles) into as many categories as you’d like. Then explain how you sorted them.

b. Sort the shapes (cut out from Template: Triangles) in another way. Then explain how you sorted them.

Guiding Questions

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Student Response

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References

EngageNY Mathematics Grade 4 Mathematics > Module 4 > Topic D > Lesson 13 — Concept Development Problem 2

Grade 4 Mathematics > Module 4 > Topic D > Lesson 13 of the New York State Common Core Mathematics Curriculum from EngageNY and Great Minds. © 2015 Great Minds. Licensed by EngageNY of the New York State Education Department under the CC BY-NC-SA 3.0 US license. Accessed Dec. 2, 2016, 5:15 p.m..

Modified by Fishtank Learning, Inc.

Problem 2

Fill out the following table based on your triangles (Template: Triangles).

Triangle Letter	Attributes (include side lengths and angle measures)	Classification
A
B
C
D
E
F
G

Guiding Questions

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Student Response

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Problem Set

15-20 minutes

Discussion of Problem Set

Which triangles in #1 are right angles? How do you know?
Look at #2. Is scalene a way of classifying a triangle by its side lengths or angles? Can we infer anything about its classification according to angle measure? Can we infer anything about its angle measures at all?
How do the tick marks and angle symbols allow classification of triangles without using tools in #3?
How did you classify the triangle in #4? Explain.
Were the statements in #5 always, sometimes, or never true? How do you know?
Were the triangles you drew in #6 more or less difficult to classify than those in #3? Why?
Explain your answer to #8b.

Target Task

A task that represents the peak thinking of the lesson - mastery will indicate whether or not objective was achieved

5-10 minutes

Problem 1

Draw lines to match each triangle below with one term that describes its sides and one term that describes its angles.

	Scalene
	Isosceles
	Equilateral
	Acute
	Right
	Obtuse

Student Response

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Problem 2

Explain how you determined how to classify triangle C.

Student Response

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Additional Practice

The Extra Practice Problems can be used as additional practice for homework, during an intervention block, etc. Daily Word Problems and Fluency Activities are aligned to the content of the unit but not necessarily to the lesson objective, therefore feel free to use them anytime during your school day.

Extra Practice Problems

Word Problems and Fluency Activities

Help students strengthen their application and fluency skills with daily word problem practice and content-aligned fluency activities.

Shapes and Angles

Objective

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Common Core Standards

Core Standards

Geometry

Geometry

Foundational Standards

Geometry

Criteria for Success

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Tips for Teachers

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Lesson Materials

Anchor Tasks

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Problem 1

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Guiding Questions

Student Response

References

Problem 2

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Guiding Questions

Student Response

Problem Set

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Discussion of Problem Set

Target Task

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Problem 1

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Student Response

Problem 2

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Student Response

Additional Practice

Extra Practice Problems

Word Problems and Fluency Activities

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