Greatest Common Factors and Prime Numbers

The video tutorial explains how to find the greatest common factor (GCF) of two or more numbers. It begins with an introduction to factors, including prime and composite numbers, and addresses common misunderstandings between factors and multiples. The tutorial provides step-by-step examples to find the GCF of 32 and 60, and then 12, 14, and 20, by listing and comparing their factors. The lesson concludes with a summary of the process for determining the GCF.

What is the first step in finding the greatest common factor of two numbers?

• List the factors of each number

• Add the numbers together

• Divide the larger number by the smaller number

• Multiply the numbers

Which of the following is a prime number?

• 21

• 15

• 7

• 9

What is the difference between factors and multiples?

• Factors are used in addition, while multiples are used in subtraction

• Factors are always even numbers, while multiples are odd

• Factors are numbers that divide another number without a remainder, while multiples are the result of multiplying a number by an integer

• Factors are larger than multiples

What is the greatest common factor of 32 and 60?

• 6

• 4

• 2

• 8

Which of the following is NOT a factor of 60?

• 15

• 12

• 7

• 5

What are the common factors of 12, 14, and 20?

• 1 and 2

• 1, 2, and 3

• 2 and 4

• 1, 2, and 4

Why is 4 not a common factor of 12, 14, and 20?

• Because 4 is not a factor of 12

• Because 4 is not a factor of 14

• Because 4 is a prime number

• Because 4 is not a factor of 20

What is the greatest common factor of 12, 14, and 20?

• 3

• 4

• 1

• 2

What is the universal factor for every whole number?

• 0

• 10

• 1

• 2

What is the main method taught in this lesson to find the greatest common factor?

• Using a calculator

• Listing and comparing factors

• Guessing the largest number

• Using a multiplication table