Fractions

Lesson 21

Math

Unit 6

3rd Grade

Lesson 21 of 24

Objective


Measure lengths to the nearest half inch.

Common Core Standards


Core Standards

  • 3.MD.B.4 — Generate measurement data by measuring lengths using rulers marked with halves and fourths of an inch. Show the data by making a line plot, where the horizontal scale is marked off in appropriate units— whole numbers, halves, or quarters.

Foundational Standards

  • 2.MD.A.1

Criteria for Success


  1. Partition an inch ruler so that each inch is partitioned into half inches.
  2. Understand how to measure an object when the 0 mark on a ruler is not flush with the ruler’s edge.
  3. Measure objects to the nearest half inch, including mixed number measurements (MP.6). 

Tips for Teachers


  • On the Problem Set, students will estimate the length of objects and then compare their estimate to the actual measurement. You could be very strategic and set out particular items that you’d like students to measure or students can find objects around the classroom on their own.
  • On the Extra Pratice Problems, students will estimate and then measure the length of various objects. Thus, students will need the same rulers that they used for the Problem Set. 

Lesson Materials

  • Template: Ruler (1 sheet per 6 students (i.e., 1 ruler per student)) — These need to be cut into individual rulers before the lesson. Students will need them for the Extra Practice Problems, as well.
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Anchor Tasks

25-30 minutes


Problem 1

Wendell and Robin are trying to measure the length of various insects in their bug collection. The measurement of an ant is shown below.  

a.   Wendell thinks the ant is about an inch long. Robin thinks the ant is closer to zero inches long. Who is correct: Wendell, Robin, both of them, or neither of them? Explain.

b.   If you were to estimate a more exact measurement of the ant’s length, about how long would you say the ant is?

Guiding Questions

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Student Response

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References

Visual: Ant Silhouette

Problem 2

Construct a half-inch ruler by partitioning each inch on the Template: Ruler into halves of an inch.

Guiding Questions

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Student Response

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References

Illustrative Mathematics Grade 3 Unit 6 Lesson 1 (Activity 2)

Activity 2, accessed on Feb. 3, 2023, 7:32 p.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 3

Measure the following objects to the nearest half inch using your ruler from Anchor Task 2. 

a.    

 

b.    

 

c.    

 

d.    

 

Guiding Questions

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Student Response

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References

EngageNY Mathematics Grade 2 Mathematics > Module 7 > End-of-Module Assessment TaskQuestion #1

Grade 2 Mathematics > Module 7 > End-of-Module Assessment Task 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 April 2, 2019, 3:52 p.m..

Modified by Fishtank Learning, Inc.

Problem Set

15-20 minutes


Discussion of Problem Set

  • How is a ruler like a number line?
  • I think the pencil in #1 is $$\frac{7}{2}$$ inches long. Do you agree or disagree? Why?
  • What made measuring the line in #2 more difficult than measuring the length of the pencil in #1?
  • What objects did you measure around the classroom in #3? Were some of your estimates more accurate than others? Why do you think that is?
  • How did you determine the length of the nail in #4?

Target Task

5-10 minutes


Measure the length of the line below to the nearest half inch.

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

Measure lengths to the nearest quarter inch.

Lesson 22
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Lesson Map

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

Topic A: Understanding Unit Fractions and Building Non-Unit Fractions

Topic B: Fractions on a Number Line

Topic C: Equivalent Fractions

Topic D: Comparing Fractions

Topic E: Line Plots

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