Rounding, Addition, and Subtraction

Lesson 3

Math

Unit 1

3rd Grade

Lesson 3 of 14

Objective


Locate three-digit numbers on a number line and explain their placement.

Common Core Standards


Core Standards

  • 3.NBT.A.1 — Use place value understanding to round whole numbers to the nearest 10 or 100.

Foundational Standards

  • 2.MD.B.6
  • 2.NBT.A.1
  • 2.NBT.A.2

Criteria for Success


  1. Understand that a number line represents numbers as lengths/distances from 0 using equally spaced tick marks or points (e.g., understand that the tick mark labeled "eight" means the distance covered by 8 length-units, rather than just the eighth length-unit).
  2. Understand the convention that a point/mark in a certain position is used to represent a number. 
  3. Identifymissing numbers on a number line by determining the interval (i.e., the distance between tick marks) and counting intervals up or back from a known position. 
  4. Identify and represent whole numbers on a number line diagram including:
  • Those with and without intervals (i.e., "open" number lines)
  • Those with intervals marked by not labeled
  • Those not starting at 0
  • Those with intervals greater than 1

Tips for Teachers


  • Students worked with number lines within 100 in Grade 2. Thus, the vocabulary here should be familiar to students. What is new in Grade 3, however, is plotting points beyond 100 on a number line.
  • There is no homework today to allow teachers to build math routines throughout the first few days of school.
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Anchor Tasks


Problem 1

a.   What do you notice? What do you wonder?

b.   Determine the value of the point on each number line in Part (a) above.

Guiding Questions

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References

Illustrative Mathematics Three-digit Numbers on the Number LineGrade 2 Unit 5 Lesson 8 Activity 1

Three-digit Numbers on the Number Line, accessed on June 6, 2022, 10:14 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.

Problem 2

a.   Label each point with the value it represents.

b.   Locate and label each number on the number line. Label the intervals with the numbers they represent if it helps.

  1. 60

 

  1. 897

 

  1. 364

 

Guiding Questions

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Problem 3

a.   Plot 55 on a number line from 50 to 60.

b.   Plot 55 on a number line from 0 to 100.

c.   Plot 55 on a number line from 0 to 1,000.

Guiding Questions

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Problem Set


Answer Keys

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Discussion of Problem Set

  • Look at #3. What made Parts (b) and (c) more challenging than Part (a)? 
  • Look at #4. How did you decide what to make your number lines look like to place 150 on them? How do your number lines look similar and different (to each other and to other students’ number lines)?
  • Look at #7. How did you determine where each value would go?

Target Task


Problem 1

Determine the value of the number shown on the number line below.

Problem 2

Show two different ways to show 285 on a number line.

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.

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Lesson 2

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Lesson 4

Lesson Map

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

Topic A: Foundations of Place Value

Topic B: Rounding to the Nearest Ten and Hundred

Topic C: Addition and Subtraction Within 1,000

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