Operations with Rational Numbers

Lesson 8

Math

Unit 2

7th Grade

Lesson 8 of 18

Objective


Find and represent the distance between two rational numbers as the absolute value of their difference.

Common Core Standards


Core Standards

  • 7.NS.A.1.C — Understand subtraction of rational numbers as adding the additive inverse, p - q = p + (-q). Show that the distance between two rational numbers on the number line is the absolute value of their difference, and apply this principle in real-world contexts.

Foundational Standards

  • 6.NS.C.7
  • 6.NS.C.8

Criteria for Success


  1. Find the distance between two values in real-world situations.
  2. Represent distance as the absolute value of the difference of the two numbers; the distance between $$p$$ and $$q$$ is represented as $$|p-q|$$.
  3. Understand that distance is a positive measurement.

Tips for Teachers


This may be a good lesson to do the How Much to 0? mental math activity, described in the 7th Grade Math Fluency Building Exercises included in this unit's materials.

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Anchor Problems

25-30 minutes


Problem 1

A man on a boat is sitting 9 feet above sea level. A bird flies at an altitude of 54 feet above sea level, and a fish swims below at an altitude of 8 feet below sea level. The ocean floor sits 75 feet below the surface of the ocean.

Find each distance described below. Then write a number sentence to represent each distance you find.

a.   Between the bird and the man

b.   Between the man and the surface of the ocean

c.   Between the man and the fish

d.   Between the ocean floor and the fish

e.   Between the ocean floor and the bird

Guiding Questions

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Student Response

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Problem 2

Aakash, Bao Ying, Chris, and Donna all live on the same street as their school, which runs from east to west.

  • Aakash lives $${5{1\over2}}$$ blocks to the west of the school.
  • Bao Ying lives $${4{1\over4}}$$ blocks to the east of the school.
  • Chris lives $${2{3\over4}}$$ blocks to the west of the school.
  • Donna lives $${6{1\over2}}$$ blocks to the east of the school.

a.   Draw a picture that represents the positions of their houses along the street.

b.   How far is each house from every other house?

c.   Represent the relative position of the houses on a number line, with the school at zero, points to the west represented by negative numbers, and points to the east represented by positive numbers.

d.   How can you see the answers to part B on the number line? Using the numbers (some of which are positive and some negative) that label the positions of houses on the number line, represent these distances using sums or differences.

Guiding Questions

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Student Response

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References

Illustrative Mathematics Distances between Houses

Distances between Houses, accessed on Aug. 14, 2017, 10:24 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 3

The distance between point Q and point R is 5.3. Give possible values for Q and R in each situation, and represent the distance on a number line.​​​​​​

a.   Q and R are both positive numbers.

 

b.   Either Q or R is negative.

 

c.   Both Q and R are negative.

 

Guiding Questions

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Student Response

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Problem Set

15-20 minutes


Give your students more opportunities to practice the skills in this lesson with a downloadable problem set aligned to the daily objective.

Target Task

5-10 minutes


The highest temperature on a winter day in New York City was $$11$$°C. The lowest temperature on the same day in the same city was $$-8$$°C.

Jordan says that over the course of the day, the temperature decreased by $$3$$°C. Do you agree with Jordan? Justify your response.

Student Response

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Additional Practice


The following resources include problems and activities aligned to the objective of the lesson that can be used for additional practice or to create your own problem set.

  • Include procedural problems where students practice finding the distance between two rational numbers.

Next

Subtract rational numbers with and without the number line.

Lesson 9
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Lesson Map

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

Topic A: Adding and Subtracting Rational Numbers

Topic B: Multiplying and Dividing Rational Numbers

Topic C: Using all Four Operations with Rational Numbers

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