Understanding Least Common Multiple (LCM)

The video tutorial explains the concept of the least common multiple (LCM) and demonstrates how to find it using factor trees. It provides a step-by-step guide, including prime factorization, listing factors, and multiplying them to get the LCM. The tutorial uses examples to clarify the process, focusing on the numbers 15 and 20, and highlights common challenges in the method.

What is the first step in finding the Least Common Multiple (LCM) according to the video?

• Divide the numbers by their greatest common divisor

• Find the prime factorization

• Add the numbers together

• Subtract the smaller number from the larger

Which of the following is NOT a step in finding the LCM as described in the video?

• Add all factors together

• Cross out common factors

• List all factors

• Create a factor tree

In the example given, what is the prime factorization of 15?

• 3 x 5

• 2 x 7

• 5 x 5

• 2 x 3

Tags

CCSS.4.OA.B.4

When creating a list of factors, what should you do if a factor appears in both numbers?

• Ignore it

• Write it once and cross it out from both lists

• Write it twice

• Only write it if it appears in the larger number

What is the prime factorization of 20 as shown in the video?

• 2 x 2 x 5

• 4 x 5

• 3 x 5

• 2 x 3 x 5

Which factor is not present in the prime factorization of 15?

• None of the above

• 5

• 3

• 2

What is the purpose of crossing out factors in the list when finding the LCM?

• To make the list shorter

• To simplify the list

• To ensure each factor is only counted once

• To eliminate unnecessary factors

What is the least common multiple of 15 and 20 as calculated in the video?

• 60

• 45

• 30

• 75

Why is the LCM of two numbers always greater than or equal to the larger of the two numbers?

• Because it is a multiple of both numbers

• Because it is the product of both numbers

• Because it is the sum of both numbers

• Because it is the difference between the two numbers

What is the result of multiplying 3, 5, and 4 in the final step of the LCM calculation?

• 45

• 60

• 75

• 90