Finding GCF and LCM of Numbers

This video tutorial explains how to find the Least Common Multiple (LCM) and Greatest Common Factor (GCF) for three or more numbers, primarily using examples with three numbers. It covers the use of factor trees to determine the GCF and a method for calculating the LCM by identifying the highest power of each prime factor. The tutorial includes several worked examples to illustrate these concepts, ranging from simple to more complex cases, and concludes with a summary of the methods discussed.

What is the first step in finding the GCF of numbers using the method described in the video?

• List all factors of each number

• Use a factor tree

• Divide the largest number by the smallest

• Multiply all numbers together

When finding the LCM, what should you do with each prime factor?

• Multiply it by the smallest number

• Use it only once

• Ignore it if it appears in only one number

• Find where it occurs most often and use it that many times

What is the GCF of the numbers 18, 20, and 24?

• 2

• 3

• 5

• 6

What is the LCM of the numbers 18, 20, and 24?

• 120

• 480

• 360

• 240

In the example with numbers 4, 9, and 12, what is the GCF?

• 1

• 2

• 4

• 3

For the numbers 12, 18, and 20, what is the LCM?

• 240

• 300

• 120

• 180

What is the GCF of the numbers 54, 96, and 9?

• 2

• 3

• 6

• 9

What is the LCM of the numbers 54, 96, and 9?

• 432

• 648

• 864

• 1080

In the example with numbers 60, 75, and 25, what is the GCF?

• 15

• 3

• 5

• 10

What is the LCM of the numbers 60, 75, and 25?

• 150

• 200

• 250

• 300