Finding GCF and LCM Concepts

This video tutorial from MooMooMath and Science explains how to find the least common multiple (LCM) and greatest common factor (GCF) of the numbers 12 and 18 using a factor tree method. The instructor demonstrates creating factor trees for both numbers, setting up a chart to list their prime factors, and then calculating the LCM and GCF. The LCM is found by multiplying the highest power of all prime factors, while the GCF is determined by multiplying the common prime factors. The video concludes with a summary of the results: the LCM is 36 and the GCF is 6.

What is the purpose of using a factor tree in finding the LCM and GCF?

• To divide the numbers

• To add the numbers

• To identify prime factors

• To simplify the numbers

Which of the following is a prime factor of 18?

• 6

• 9

• 3

• 4

What is the first step in setting up the chart for organizing prime factors?

• Identify the prime factors

• Draw a factor tree

• List all factors of 18

• Write down the number 12

When calculating the LCM, what should you do if you have two of the same numbers?

• Ignore them

• Bring down only one

• Add them together

• Multiply them

What is the LCM of 12 and 18?

• 24

• 36

• 48

• 60

What is the rule for finding the GCF of two numbers?

• Identify common prime factors

• Subtract the smaller number from the larger

• Multiply all numbers

• Add all prime factors

Which prime numbers are common in both 12 and 18?

• 3 and 4

• 2 and 3

• 3 and 5

• 2 and 5

What is the GCF of 12 and 18?

• 6

• 4

• 3

• 2

Why is it important to identify prime numbers in both numbers when finding the GCF?

• To ensure accuracy

• To simplify calculations

• To find common factors

• To avoid mistakes

What should you do after identifying the common prime factors for the GCF?

• Multiply them

• Subtract them

• Add them together

• Divide them