Shapes and Angles

Lesson 7

Math

Unit 8

4th Grade

Lesson 7 of 18

Objective


Measure angles that are less than 180° using a 180° protractor. Distinguish angle measure from other attributes.

Common Core Standards


Core Standards

  • 4.MD.C.5 — Recognize angles as geometric shapes that are formed wherever two rays share a common endpoint, and understand concepts of angle measurement:
  • 4.MD.C.6 — Measure angles in whole-number degrees using a protractor. Sketch angles of specified measure.

Criteria for Success


  1. Distinguish angle measure from other attributes, such as the length of the line segments that make up the angle, the distances between their endpoints, the area of the triangles determine by the drawn arms, etc. 
  2. Estimate the measurement of angles based on their proximity to various benchmark angles (45°, 60°, 90°, etc.).
  3. Measure angles less than 180° with protractors, placing the middle notch on the vertex of the angle, aligning a side with the zero or base line on the protractor, and reading the number the second side length touches (MP.5, MP.6). 
  4. Measure angles with short rays by extending the rays (which can be done since the length of the rays does not determine the angle measure).
  5. Construct viable arguments and critique the reasoning of others regarding the reasonableness of an angle measurement by comparing the estimated measurement based on benchmark angles to the actual measurement (MP.3). 
  6. See that angle measure is the same regardless of what protractor is being used to measure.

Tips for Teachers


  • Students will need a protractor for the Problem Set. It is recommended that you have students estimate all of the angle measures first, and then hand them a protractor when they are done. This will help students build visual models of benchmark fractions. 
  • Students will need a protractor for the Extra Practice Problems.

Lesson Materials

  • 180° Protractor (1 per student)
  • Circular protractor (1 per teacher)
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Anchor Tasks

25-30 minutes


Problem 1

Below are three angles, $$\angle A$$$$\angle B$$ and $$\angle C$$.

Which angle has the greatest measure? How do you know?

Guiding Questions

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Student Response

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Problem 2

a.   Estimate the measure of each angle in Anchor Task 1.

b.   Using a 180° protractor, find the exact measure of each angle in Anchor Task 1.

Guiding Questions

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Student Response

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Problem 3

a.   Use a 180° protractor to find the measure of each angle in degrees.

  1.  

  1.  

  1.  

  1.  

b.   Use a 180° protractor to measure the labeled angles in each figure.

Guiding Questions

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Student Response

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References

Illustrative Mathematics Grade 4 Unit 7 Lesson 10 Activity 1

Grade 4 Unit 7 Lesson 10 Activity 1, accessed on Oct. 16, 2023, 8:39 a.m., is licensed by Illustrative Mathematics under either the CC BY 4.0 or CC BY-NC-SA 4.0. For further information, contact Illustrative Mathematics.

Modified by Fishtank Learning, Inc.

Problem Set

15-20 minutes


Discussion of Problem Set

  • Look at #1. How did you determine the angle measure without using a protractor? How can this skill help you when using an actual protractor to measure? 
  • In #2, which angle had the same measure as $${\angle G}$$?  $${\angle I}$$?
  • In #2, which angles had the same angle measure but different side length measures?
  • For #3, discuss your experience of measuring with different protractors. Describe how the length of an arc on each protractor did or did not affect the measure of the given angle.
  • Take a look at your 180° protractor. Find pairs of numbers that label the two scales, such as 150° and 30°. Name other pairs of numbers. What do you notice about the pairs of numbers?

Target Task

5-10 minutes


First, estimate the measure of each angle below. Then, use a protractor to find their measure, in degrees.

a.   

Estimate: __________

Measurement: __________

b.   

Estimate: __________

Measurement: __________

c.   

Estimate: __________

Measurement: __________

d.   

Estimate: __________

Measurement: __________

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.

Word Problems and Fluency Activities

Word Problems and Fluency Activities

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

Next

Sketch angles of specified measure using a 180° protractor.

Lesson 8
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Lesson Map

A7CB09C2-D12F-4F55-80DB-37298FF0A765

Topic A: Lines and Angles

Topic B: Measures of Angles

Topic C: Measures of Adjacent Angles

Topic D: Shapes and Lines of Symmetry

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