Factors and Common Factors of Numbers

The video tutorial explains how to find the greatest common factor (GCF) of two numbers, 28 and 42. It begins by listing all the factors of each number. For 28, the factors are 1, 2, 4, 7, 14, and 28. For 42, the factors are 1, 2, 3, 6, 7, 14, 21, and 42. The tutorial then identifies the greatest factor common to both numbers, which is 14, and concludes that 14 is the GCF.

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

• Add the numbers together

• Divide the numbers by each other

• List all the factors of each number

• Multiply the numbers

Which of the following is a factor of 28?

• 20

• 14

• 9

• 5

How can you express 28 as a product of two numbers?

• 5 * 6

• 1 * 28

• 7 * 5

• 3 * 9

Which of the following is NOT a factor of 28?

• 9

• 1

• 4

• 7

What is the largest factor of 28?

• 21

• 14

• 7

• 28

What is the smallest factor of 42?

• 3

• 2

• 6

• 1

Which of the following pairs of numbers multiply to give 42?

• 5 * 8

• 2 * 21

• 3 * 15

• 4 * 10

Which of the following is NOT a factor of 42?

• 1

• 3

• 7

• 5

How can you express 42 as a product of two numbers?

• 3 * 13

• 1 * 42

• 4 * 11

• 2 * 20

What is the largest factor of 42?

• 21

• 28

• 14

• 42