Teaching LCM and GCF Using the Ladder Method

Rachel Kov explains how to teach the Least Common Multiple (LCM) and Greatest Common Factor (GCF) using the latter method. She demonstrates the process with the numbers 24 and 36, showing how to find the smallest prime numbers and use them to calculate the LCM and GCF. The LCM is found by multiplying all numbers in the L shape, while the GCF is determined by multiplying numbers straight down the line. The video concludes with a summary of the method.

What two numbers are used to demonstrate the ladder method for finding LCM and GCF?

• 12 and 18

• 24 and 36

• 6 and 9

• 2 and 3

What is the first prime number used in the ladder method for the numbers 24 and 36?

• 7

• 2

• 5

• 3

After the first division step using the number 2, what are the resulting numbers?

• 24 and 36

• 6 and 9

• 12 and 18

• 2 and 3

Tags

CCSS.4.OA.B.4

What prime number is used after the number 2 no longer divides both numbers?

• 2

• 7

• 3

• 5

What are the final prime numbers obtained after all divisions in the ladder method?

• 2, 2, 3, 3

• 2, 2, 2, 3

• 2, 3, 3

• 2, 2, 3

How is the LCM calculated using the ladder method?

• By adding all numbers

• By multiplying all numbers on the L

• By dividing the largest number

• By subtracting the smallest number

What is the LCM of 24 and 36 using the ladder method?

• 12

• 36

• 144

• 72

How is the GCF found using the ladder method?

• By subtracting the numbers

• By dividing the numbers

• By adding the numbers straight down the line

• By multiplying the numbers straight down the line

What is the GCF of 24 and 36 as found using the ladder method?

• 24

• 6

• 36

• 12