Operations with Rational Numbers

Lesson 9

Math

Unit 2

7th Grade

Lesson 9 of 18

Objective


Subtract rational numbers with and without the number line.

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.
  • 7.NS.A.1.D — Apply properties of operations as strategies to add and subtract rational numbers.

Foundational Standards

  • 6.NS.C.7

Criteria for Success


  1. Write subtraction problems for real-world situations.
  2. Write and understand subtraction problems as addition problems of the opposite value.
  3. Find differences of rational numbers with and without using the number line.

Tips for Teachers


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Anchor Problems

25-30 minutes


Problem 1

Mount Ojos del Salado is the highest mountain in Chile, with a peak at about 6,900 meters above sea level. The Atacama Trench, just off the coast of Peru and Chile, is about 8,100 meters below sea level (at its lowest point).

a.   What is the difference in elevations between Mount Ojos del Salado and the Atacama Trench?

b.   Is the elevation halfway between the peak of Mount Ojos del Salado and the Atacama Trench above sea level or below sea level? Explain without calculating the exact value.

c.   What elevation is halfway between the peak of Mount Ojos del Salado and the Atacama Trench?

Guiding Questions

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Student Response

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References

Illustrative Mathematics Differences of Integers

Differences of Integers, accessed on Aug. 14, 2017, 11:15 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

Find each sum or difference. Rewrite subtraction problems into addition problems or use a number line as needed.

a.       $${18{1\over5}-(-5)}$$

b.    $${-40{2\over3}-8{1\over2}}$$

c.   $${-9.08+16.52}$$

d.       $${-6-(-12)}$$

e.       $${-11{1\over6}-(-3)}$$

f.   $${52+(-15)}$$

g.   $${-36.125+(-14.6)}$$

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


Problem 1

Which pair of expressions below are equivalent?

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Student Response

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Problem 2

Tasia's bank account was –$25.64. She deposited a check into her bank account and her new total is $152.29. How much was the check that Tasia deposited into her account?

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 practice with subtracting rational numbers, including integers, decimals, and fractions.

Next

Add and subtract rational numbers efficiently using properties of operations.

Lesson 10
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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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