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Chapter 4 Section 1
Math Learning Goal
Students will
understand number
theory and fractions.
4-1 Divisibility
Today’s Learning Goal Assignment
Learn to use
divisibility
rules.
Course 1
Students will understand number theory and fractions by
being able to do the following:
• Learn to use divisibility rules (4-1)
4-1 Divisibility
th
6
Grade Math HW
Page 154
#9-28
Course 1
4-1 Divisibility
Lesson Presentation
Course 1
http://my.hrw.com/index.jsp
CHAPTER CAREER &
ARE YOU READY?
http://www.khanacademy.org/
math/arithmetic/factorsmultiples/v/recognizingdivisibility
KAHN ACADEMY
RECOGNIZING DIVISIBILITY
4-1 Divisibility
Today’s Learning Goal Assignment
Learn to use
divisibility
rules.
Course 1
4-1 Divisibility
Insert Lesson Title Here
Vocabulary
divisibility
composite number
prime number
Course 1
4-1 Divisibility
A number is divisible by another
number if the quotient is a whole
number with no remainder.
42 ÷ 6 = 7
Course 1
Quotient
4-1 Divisibility
Divisibility Rules
A number is divisible by. . .
Divisible
Not Divisible
2
if the last digit is even (0, 2, 4, 6, or 8).
3,978
4,975
3
if the sum of the digits is divisible by 3.
315
139
4
if the last two digits form a number
divisible by 4.
8,512
7,518
5
if the last digit is 0 or 5.
14,975
10,978
6
if the number is divisible by both 2 and 3
48
20
9
if the sum of the digits is divisible by 9.
711
93
15,990
10,536
10 if the last digit is 0.
Course 1
4-1 Divisibility
Additional Example 1A: Checking Divisibility
Tell whether 462 is divisible by 2, 3, 4, and 5.
2
The last digit, 2, is even.
3
The sum of the digits is 4 + 6 + 2 = 12.
Divisible
12 is divisible by 3.
4
The last two digits form the number 62.
62 is not divisible by 4.
Not
divisible
5
The last digit is 2.
Not
divisible
So 462 is divisible by 2 and 3.
Course 1
Divisible
4-1 Divisibility
Try This: Example 1A
Tell whether 114 is divisible by 2, 3, 4, and 5.
2
The last digit, 4, is even.
Divisible
3
The sum of the digits is 1 + 1 + 4 = 6.
6 is divisible by 3.
Divisible
4
The last two digits form the number 14.
14 is not divisible by 4.
Not
Divisible
The last digit is 4.
Not
Divisible
5
So 114 is divisible by 2 and 3.
Course 1
4-1 Divisibility
Additional Example 1B: Checking Divisibility
Tell whether 540 is divisible by 6, 9, and 10.
6
The number is divisible by both
2 and 3.
Divisible
9
The sum of the digits is 5 + 4 + 0 = 9.
9 is divisible by 9.
Divisible
The last digit is 0.
Divisible
10
So 540 is divisible by 6, 9, and 10.
Course 1
4-1 Divisibility
Try This: Example 1B
Tell whether 810 is divisible by 6, 9, and 10.
6
The number is divisible by both
2 and 3.
Divisible
9
The sum of the digits is 8 + 1 + 0 = 9.
9 is divisible by 9.
Divisible
The last digit is 0.
Divisible
10
So 810 is divisible by 6, 9, and 10.
Course 1
4-1 Divisibility
Any number greater than 1 is divisible by at
least two numbers—1 and the number itself.
Numbers that are divisible by more than two
numbers are called composite numbers.
A prime number is divisible by only the
numbers 1 and itself. For example, 11 is a
prime number because it is divisible by only
1 and 11. The numbers 0 and 1 are neither
prime nor composite.
Course 1
http://teachertube.com/view
Video.php?video_id=85194
PRIME AND COMPOSITE
NUMBERS
4-1 Divisibility
Click to see which numbers from 1 through 50
are prime.
1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30
31 32 33 34 35 36 37 38 39 40
41 42 43 44 45 46 47 48 49 50
Course 1
4-1 Divisibility
Additional Example 2A & 2B: Identifying Prime and
Composite Numbers
Tell whether each number is prime or
composite.
A. 23
divisible by 1, 23
prime
B. 48
divisible by 1, 2, 3, 4, 6, 8, 12, 16, 24, 48.
composite
Course 1
4-1 Divisibility
Try This: Example 2A & 2B
Tell whether each number is prime or
composite.
A. 27
divisible by 1, 3, 9, 27
composite
B. 24
divisible by 1, 2, 3, 4, 6, 8, 12, 24
composite
Course 1
4-1 Divisibility
Additional Example 2C & 2D: Identifying Prime and
Composite Numbers
Tell whether each number is prime or
composite.
C. 31
divisible by 1, 31
prime
D. 18
divisible by 1, 2, 3, 6, 9, 18
composite
Course 1
4-1 Divisibility
Try This: Example 2C & 2D
Tell whether each number is prime or
composite.
C. 11
divisible by 1, 11
prime
D. 8
divisible by 1, 2, 4, 8
composite
Course 1
4-1 Divisibility
Insert Lesson Title Here
Lesson Quiz
Tell whether each number is divisible by 2,
3, 4, 5, 6, 9, and 10.
1. 256
divisible by 2, 4
2. 720
divisible by 2, 3, 4, 5, 6, 9, 10
3. 615
divisible by 3, 5
Tell whether each number is prime or
composite.
4. 47 prime
Course 1
5. 38 composite
http://teachertube.com/vi
ewVideo.php?title=Rules_
for_divisibility_NEW__&vi
deo_id=191367
RULES FOR DIVISIBILITY SONG