Pythagorean Theorem and Volume

Lesson 5

Math

Unit 7

8th Grade

Lesson 5 of 16

Objective


Represent decimal expansions as rational numbers in fraction form.

Common Core Standards


Core Standards

  • 8.NS.A.1 — Know that numbers that are not rational are called irrational. Understand informally that every number has a decimal expansion; for rational numbers show that the decimal expansion repeats eventually, and convert a decimal expansion which repeats eventually into a rational number.

Foundational Standards

  • 7.NS.A.2.D
  • 7.NS.A.3

Criteria for Success


  1. Understand that decimals that terminate or repeat are rational numbers and can be represented in the form $${a\over{b}}$$, where $$a$$ and $$b$$ are integers, and $$b\neq0$$.
  2. Write decimal expansions, those that terminate and those that repeat, as fractions. 
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Anchor Problems

25-30 minutes


Problem 1

Write each rational number in the form $${a\over{b}}$$, where $$a$$ and $$b$$ are integers, and $$b\neq0$$.

a.   $${0.3333}$$

b.   $${-5.05}$$

c.   $${\sqrt{64}}$$

e.   $${\sqrt{4\over25}}$$

f.   $${\sqrt{1.21}}$$

Guiding Questions

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Student Response

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Problem 2

A student wrote two repeating decimals as fractions using the strategy shown below. 

Given the decimal $$0.\overline{12}$$

Let $$x=0.\overline{12}$$

Then $$100x=12.\overline{12}$$

Given the decimal $$0.\overline{123}$$

Let $$x=0.\overline{123}$$

Then $$1000x=123.\overline{123}$$

a.   Describe the student’s strategy in your own words.

b.   Use the same strategy to write the two decimals below as fractions. 

  1.  $${0.\overline{54}}$$
  2. $${0.1\overline{23}}$$

Guiding Questions

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Student Response

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Problem 3

What is the sum of $${0.1}$$ and $${0.\overline3}$$ written as a fraction?

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


Write each decimal expansion as a rational number in the form $${a\over b}$$, where $$a$$ and $$b$$ are integers.

a.   $${0.61313}$$

b.   $${0.6\overline{13}}$$

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.

Next

Understand the Pythagorean Theorem as a relationship between the side lengths in a right triangle.

Lesson 6
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Lesson Map

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

Topic A: Irrational Numbers and Square Roots

Topic B: Understanding and Applying the Pythagorean Theorem

Topic C: Volume and Cube Roots

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