Lesson plan

# Lesson 13: Cube Roots

teaches Common Core State Standards MP3 http://corestandards.org/Math/Practice/MP3
teaches Common Core State Standards 8.NS.A.2 http://corestandards.org/Math/Content/8/NS/A/2
teaches Common Core State Standards 8.EE.A.2 http://corestandards.org/Math/Content/8/EE/A/2

# Lesson 13: Cube Roots

In this lesson, students continue to work with cube roots, moving away from the geometric interpretation in favor of the algebraic definition. They approximate cube roots and locate them on the number line. They see their first negative cube root, and locate it on the number line.

Lesson overview

• 13.1 Warm-up: True or False: Cubed (5 minutes)
• 13.2 Activity: Cube Root Values (10 minutes)
• 13.3 Activity: Solutions on a Number Line (10 minutes)
• Includes "Are you Ready for More?" extension problem
• Lesson Synthesis
• 13.4 Cool-down: Different Types of Roots (5 minutes)

Learning goals:

• Determine the whole numbers that a cube root lies between, and explain (orally) the reasoning.
• Generalize a process for approximating the value of a cube root, and justify (orally and in writing) that if $$x^3=a$$, then $$x=\sqrt[3]{a}$$.

Learning goals (student facing):

• Let’s compare cube roots.

Learning targets (student facing):

• When I have a cube root, I can reason about which two whole numbers it is between.

Required materials:

• colored pencils

Glossary:

• Access the complete Grade 8 glossary.

IM 6–8 Math was originally developed by Open Up Resources and authored by Illustrative Mathematics, and is copyright 2017-2019 by Open Up Resources. It is licensed under the Creative Commons Attribution 4.0 International License (CC BY 4.0). OUR's 6–8 Math Curriculum is available at https://openupresources.org/math-curriculum/.