# 9.21 - msdiehl7math

```REMEMBER! Do not turn in your HW this morning. We
will be going over the worksheet and using it for HW
tonight!
Do Now 1 (5 min)
1.
2.
3.
4.
Define a square root.
What is the square root of 81?
What is five squared?
What is the difference between perfect
and imperfect squares?
• To cube a number, you multiply it by itself
three times.
• Example: 3 Cubed (33) =3 × 3 × 3 = 27
Perfect Cubes
Perfect Cube = a whole number that is formed
by multiplying one whole number by itself
three times.
Example:
27 is a perfect cube because…
3 x 3 x 3 = 27
• The cube root of 27
Cube
3
27 = 3
27

3
3 x 3 x 3 = 27
Cube Root
• The cube root of 64
Cube
3
64 = 4
64

4
4 x 4 x 4 = 64
Cube Root
Root
Perfect Cube
1 2
1 8
3
27
4
64
5
6
125 216
Root
7
Perfect
MemorizeCube
or not?
343 512 729 1,000
8
You will have a copy of this for estimation!!
9
10
STOP AND JOT 1
1.) How else can we write 5 x 5 x 5?
2.) How else can we write “the cube root of
216”?
3.) What is a perfect cube?
4.) What is a perfect cube root?
Imperfect Cubes/Roots
Imperfect Cube = a whole number that is
formed by multiplying one non-whole number
by itself three times.
Example:
40 is an imperfect cube because…
3.4 x 3.4 x 3.4 = 40
• The cube root of 40
Cube
3
40= 3.4
40

3.4
3.4 x 3.4 x 3.4 = 40
Cube Root
Root
Perfect Cube
1 2
1 8
3
27
4
64
5
6
125 216
Steps:
1)Refer to perfect cubes close to the number you
are estimating.
2)Make an estimation using the number line.
Root
Perfect Cube
1 2
1 8
3
27
4
64
5
6
125 216
--Problem: 3 40
--We look between 64 and 27.
--Since 40 is about in the middle of 27 and 64, we
are looking for a root roughly in the middle of 3
and 4.

Stop and Jot 2
• Use the chart to estimate
Root
Perfect Cube
1 2
1 8

3
3
27
70
4
64
5
6
125 216
“Show what you know!”
Root
2
3 3 704
• Use the chart 1
to estimate
Perfect Cube
1 8
27 64
A.)
3
216
B.)
3
200
C.)
3
17
1.) 5
1.) 5
1.) 2.1
2.) 4

2.) 6
2.) 2.9
3.) 5.5
3) 5.8
3.) 3.0
4) 6
4.) 4.9
4) 2.6
5
6
125 216
EXIT TICKET
1.) What is a cube root?
2.) What is the difference between a perfect
cube and an imperfect cube?
3.) 3 27
4.) 3 80
5.) 3
205
Root
Perfect Cube
1 2
1 8
3
27
4
64
5
6
125 216
7 estimate
8
•Root
Use the chart to
Perfect Cube
4.)
3
400
5.)
3
800
6.)
3
500
970 10
51
1,00
343
729
2
0

3
```