Download Greatest Common Factor

Jon and Elly are making treat bags
for their class party.
Jon brought 32 pieces of gum.
Elly brought 40 mints.
What is the greatest number
of equal treat bags they can make?
In this lesson you will learn how
to find the
greatest common factor of two
whole numbers
by listing factor pairs.
Let’s Review
Factors are numbers multiplied together
to equal a product.
For example:
3 x 4 = 12
Both 3 and 4 are factors of 12.
3 x 4 is a factor pair.
Let’s Review
Factor Pairs of 12
1
x
12
2
x
6
3
4
x
x
4
3
6
12
x
x
2
1
Let’s Review
Factor Pairs of 18
1
x
18
2
x
9
3
6
x
x
6
3
9
18
x
x
2
1
Core Lesson
3 steps to finding the
Greatest Common Factor
1. List the factor pairs.
2. Identify the common factors.
3. Find the biggest common factor.
That is the Greatest Common Factor (GCF)
Core Lesson
Compare the factor pairs of 12 and 18.
Factor Pairs of 12
1. List factor pairs
1
x
12
2
x
3
x
2. Find common factors
4
x
6
x
12
x
3. Find GCF
6
4
3
2
1
Factor Pairs of 18
1
x
18
2
3
6
9
18
1, 2, 3, and 6
x
x
x
x
x
9
6
3
2
1
Jon and Elly are making treat bags
for their class party.
Jon brought 32 pieces of gum.
Elly brought 40 mints.
What is the greatest number
of equal treat bags they can make?
Core Lesson
Find the greatest common factor of 32 and 40.
1. List factor pairs
Factor Pairs of 32
1
x
32
1
x
40
2
x
16
2
x
20
4
x
8
4
x
10
8
x
4
5
x
8
16
x
2
8
x
5
32
x
1
10
x
4
20
x
2
40
x
1
2. Find common factors
3. Find GCF
Factor Pairs of 40
1, 2, 4, 8
Core Lesson
Jon brought 32 pieces of gum.
Factor Pairs of 32
# of bags
# of treats
1
x
32
2
x
16
4
x
8
8
x
4
16
x
2
32
x
1
4 gum
4 gum
4 gum
4 gum
4 gum
4 gum
4 gum
4 gum
Core Lesson
Elly brought 40 mints.
Factor Pairs of 40
# of bags
# of treats
1
x
40
2
x
20
4
x
10
5
x
8
8
x
5
10
x
4
20
x
2
40
x
1
5 mints
5 mints
5 mints
5 mints
5 mints
5 mints
5 mints
5 mints
Core Lesson
Jon and Elly can combine bags.
4 gum
4 gum
4 gum
4 gum
4 gum
4 gum
4 gum
4 gum
4 gum
4 gum
4 gum
4 gum
4 gum
4 gum
4 gum
4 gum
5 mints 5 mints 5 mints 5 mints 5 mints 5 mints 5 mints 5 mints
5 mints
The greatest number of equal treat bags
Jon and Elly can make is 8.
5 mints
5 mints
5 mints
5 mints
5 mints
5 mints
5 mints
In this lesson you have learned
how to find the greatest common
factor
of two whole numbers
by listing factor pairs.