Finding LCM and GCF Concepts

This video tutorial explains how to find the greatest common factor (GCF) and the lowest common multiple (LCM) of the numbers 60 and 24. It begins with finding the GCF using a factor tree to identify prime factors, then demonstrates how to use these factors to calculate the GCF. The video continues by using the same prime factors to find the LCM, explaining the process of selecting and multiplying the appropriate factors. The tutorial concludes with a summary of the results: the GCF is 12, and the LCM is 120.

What two numbers are we finding the LCM and GCF for in this video?

• 60 and 24

• 50 and 20

• 70 and 30

• 80 and 40

What is the first step in using a factor tree for the number 60?

• Divide by 3

• Divide by 4

• Divide by 2

• Divide by 5

Tags

CCSS.4.OA.B.4

Which of the following is a prime factor of 24?

• 9

• 2

• 7

• 5

What is the purpose of creating a chart with prime factors?

• To find the sum of the numbers

• To multiply the numbers directly

• To divide the numbers

• To list all prime factors for comparison

How do you determine the GCF from the prime factor chart?

• Divide the numbers

• Find pairs and multiply one from each pair

• Multiply all the numbers

• Add all the numbers

What is the GCF of 60 and 24?

• 10

• 8

• 12

• 6

What is the rule for selecting numbers in the LCM calculation?

• Bring down all numbers

• Bring down only one number from each pair

• Bring down only even numbers

• Bring down only odd numbers

What is the LCM of 60 and 24?

• 110

• 120

• 100

• 130

Which number is not brought down in the GCF calculation but is in the LCM?

• 5

• 7

• 3

• 2

What is the final step in finding the LCM?

• Divide the numbers

• Add all the numbers

• Subtract the numbers

• Multiply the selected numbers