Finding GCF and LCM with Factor Trees

This video tutorial explains how to find the greatest common factor (GCF) and least common multiple (LCM) using factor trees. It begins with simple examples using numbers like 10 and 25, and progresses to more complex numbers such as 24 and 42, and finally 18 and 36. The tutorial emphasizes the importance of identifying shared factors and using multiplication to determine the LCM. The method is presented as an easy and reliable way to calculate GCF and LCM, with a focus on understanding the underlying principles.

What is the first step in finding the Greatest Common Factor (GCF) using a factor tree?

• Multiply the numbers together

• List all the prime factors of each number

• Find the least common multiple

• Add the numbers together

Which of the following is a prime factor of 10?

• 6

• 2

• 4

• 8

Tags

CCSS.4.OA.B.4

What is the Greatest Common Factor (GCF) of 10 and 25?

• 10

• 5

• 2

• 25

How do you find the Least Common Multiple (LCM) using a factor tree?

• Divide the larger number by the smaller number

• Subtract the smaller number from the larger number

• Multiply one number by the factors in the box of the other number

• Add the numbers together

What is the Least Common Multiple (LCM) of 10 and 25?

• 100

• 50

• 25

• 10

Which of the following is a common factor of 24 and 42?

• 2

• 4

• 8

• 6

What is the Greatest Common Factor (GCF) of 24 and 42?

• 2

• 4

• 6

• 8

What is the Least Common Multiple (LCM) of 24 and 42?

• 84

• 210

• 126

• 168

What is the Greatest Common Factor (GCF) of 18 and 36?

• 6

• 36

• 9

• 18

What is the Least Common Multiple (LCM) of 18 and 36?

• 18

• 36

• 54

• 72