Understanding LCM through Factor Trees

This video tutorial explains how to find the least common multiple (LCM) of 18 and 21 using factor trees. It begins with an introduction to the concept of LCM and the use of factor trees. The video then demonstrates creating factor trees for the numbers 18 and 21, identifying their prime factors. A prime number chart is constructed to organize these factors. The tutorial concludes with the calculation of the LCM by multiplying the necessary prime factors, resulting in an LCM of 126. The video ends with a call to action for viewers to subscribe and share.

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

• To simplify the numbers

• To identify the prime factors

• To add the numbers

• To divide the numbers

Which of the following is a prime factor of 18?

• 4

• 5

• 2

• 6

What is the result of multiplying the prime factors of 18?

• 18

• 12

• 9

• 15

Which of the following is a prime factor of 21?

• 9

• 8

• 5

• 3

What is the result of multiplying the prime factors of 21?

• 18

• 21

• 14

• 10

What is the LCM of 18 and 21?

• 108

• 84

• 90

• 126

Which rule is applied when combining prime factors to find the LCM?

• Use all numbers twice

• Use only the largest number

• Use one number from each vertical pair

• Use only even numbers