Lesson 13Cube Roots
Learning Goal
Let’s compare cube roots.
Learning Targets
When I have a cube root, I can reason about which two whole numbers it is between.
Lesson Terms
- cube root
Warm Up: True or False: Cubed
Problem 1
Decide if each statement is true or false.
Activity 1: Cube Root Values
Problem 1
What two whole numbers does each cube root lie between? Be prepared to explain your reasoning.
Activity 2: Solutions on a Number Line
Problem 1
The numbers
Plot
, , and on the number line. Be prepared to share your reasoning with the class. Plot
on the number line.
Are you ready for more?
Problem 1
Diego knows that
Is he correct? Explain how you know.
Lesson Summary
Remember that square roots of whole numbers are defined as side lengths of squares. For example,
We can approximate the values of cube roots by observing the whole numbers around it and remembering the relationship between cube roots and cubes. For example,
Also like square roots, most cube roots of whole numbers are irrational. The only time the cube root of a number is a whole number is when the original number is a perfect cube.