Finding the Greatest Common Factor

The video tutorial explains how to find the greatest common factor (GCF) of two numbers using prime factorization. It demonstrates the process with examples of 18 and 24, and 72 and 90, by creating factor trees and identifying common prime factors. The tutorial emphasizes understanding multiplication tables and provides a foolproof method for determining the GCF.

What is the greatest common factor (GCF) of two numbers?

• The sum of the two numbers

• The largest number that divides both numbers

• The smallest number that divides both numbers

• The difference between the two numbers

Which of the following is a prime factor of 18?

• 9

• 4

• 6

• 3

What is the prime factorization of 24?

• 2 x 2 x 3

• 2 x 2 x 2 x 3

• 2 x 3 x 3

• 3 x 3 x 3

What is the GCF of 18 and 24?

• 8

• 6

• 4

• 12

What is the first step in the foolproof method for finding the GCF?

• Multiply the two numbers

• Add the two numbers

• Subtract the smaller number from the larger

• Find the prime factors of each number

Which pair of numbers can be used to start the factor tree for 72?

• 5 and 14

• 7 and 10

• 6 and 12

• 8 and 9

What is the prime factorization of 90?

• 2 x 5 x 5

• 2 x 3 x 3 x 5

• 2 x 2 x 3 x 5

• 3 x 3 x 5

How many factors of 3 are common between 72 and 90?

• None

• Three

• Two

• One

What is the GCF of 72 and 90?

• 18

• 36

• 24

• 12

Which of the following is NOT a step in finding the GCF using prime factorization?

• Identify common prime factors

• Multiply the common prime factors

• Add the prime factors

• Create a factor tree