Lesson 1 PACE WORK Form 8D Theme:The Greatest Common Factor

 Monday, the eleventh of January

Theme: The Greatest Common Factor

Presentation of new material

T.: Now, I'll give you some cards (card#1) and you should read and study the rules.

The "Greatest Common Factor" is the largest of the common factors (of two or more numbers)

Finding the Greatest Common Factor

Here are three ways:

1. You can:

find all factors of both numbers (I have an All Factors Calculator to help you),

then select the ones that are common to both, and

then choose the greatest.

2. You can find the prime factors and combine the common ones together.

3. And sometimes you can just play around with the factors until you discover it.

T.: When you find all the factors of two or more numbers, and you find some factors are the same ("common"), the largest of those common factors is the Greatest Common

Factor (GCF).

Now, please, answer the questions:

What are the factors of 12?          1, 2, 3, 4, 6, and 12

What are the factors of 20?          1, 2, 4, 5, 10, and 20

Which are the common factors?   1, 2, and 4

What is the GCF?  

T.: You have got the cards (card#2). You should find the Greatest Common Factor.  

Card#1

Read and study the rules:

The "Greatest Common Factor" is the largest of the common factors (of two or more numbers)

Finding the Greatest Common Factor

Here are three ways:

1. You can:

find all factors of both numbers (I have an All Factors Calculator to help you),

then select the ones that are common to both, and

then choose the greatest.

2. You can find the prime factors and combine the common ones together.

3. And sometimes you can just play around with the factors until you discover it.

 

Example: Find the GCF of 18 and 27

The factors of 18 are 1, 2, 3, 6, 9, 18.

The factors of 27 are 1, 3, 9, 27.

The common factors of 18 and 27 are 1, 3 and 9.

The greatest common factor of 18 and 27 is 9.

Card#2

1. Find the GCF of each set of numbers.

 a) 12, 78 6     

b) 40, 50 10

c) 20, 45 5

d)32, 48, 16

e) 36, 60, 84

2. Which set of numbers has the greatest

GCF?

 a) 4, 5, 20

 b)18, 36

 c) 18, 36, 45

 d) 23, 29

3. In a marching band, there are 64 woodwinds, 88 brass, and 16 percussion

players. When they march in a parade, there is the same number of students in

each row.

a) Find the greatest number of students in each row.

b) How many rows of each group are there?