Transcript Course 2 Lesson 5

Lesson 5-2
Pages 203-206
Greatest Common
Factor
Lesson Check 5-1
What you will learn!
How to find the greatest
common factor of two or
more numbers.
Greatest common factor (GCF)
What you really need to know!
The greatest common factor
(GCF) of two or more
numbers is the largest
number that is a factor of
each number. The GCF of
prime numbers is 1.
Example 1: Method 1
Find the GCF of 28 and 42.
Common
Factors
28
42
1 x 28 1 x 42 1
2 x 14 2 x 21 2
4 x 7 3 x 14 7
6 x 7 14
GCF
14
Example 1: Method 2
Find the GCF of 28 and 42.
28 = 2 x 2 x 7
42 = 2 x 3 x 7
2
x
7 = 14 GCF
Example 2: Method 2
Find the GCF of 20 and 32.
20 = 2 x 2 x 5
32 = 2 x 2 x 2 x 2 x 2
2 x 2 = 4 GCF
Example 3:
Find the GCF of 21, 42 and 63.
21 = 3 x 7
42 = 2 x 3 x 7
63 = 3 x 3 x 7
3 x 7 = 21 GCF
Example 4:
Find the GCF:
2•2•3•y•y
3
30y = 2 • 3 • 5 • y • y • y
2
12y =
2•3•y•y=
2
6y
Example 5:
Searra wants to cut a 15 cm by
25 cm piece of tag board into
squares for an art project. She
does not want to waste any of
the tag board and she wants the
largest squares possible. What
is the length of the side of the
squares she should use?
15 = 3 x 5
25 = 5 x 5
The squares should
be 5cm on each side.
Page 205
Guided Practice
#’s 4-8
Read:
Pages 203-204
with someone at
home and study
examples!
Homework: Page 205-206
#’s 10-32 even
#’s 38-51
Lesson Check 5-2
Page
574
Lesson 5-2
Lesson Check 5-2