Finding LCM and GCF with the Ladder Method

What is the first step in the ladder method?

• Subtract the numbers

• Add the numbers

• Multiply the numbers

• Flip the division sign upside down

Which numbers are we working with in this tutorial?

• 25 and 40

• 15 and 21

• 30 and 42

• 20 and 35

What number goes evenly into both 30 and 42?

• 5

• 7

• 3

• 2

What are the results after dividing 30 and 42 by 2?

• 15 and 21

• 10 and 20

• 15 and 20

• 10 and 21

What is the next common factor for 15 and 21?

• 5

• 3

• 7

• 2

What do you do when there are no more common factors?

• Divide the numbers again

• Highlight or circle the numbers

• Multiply the remaining numbers

• Stop the process

How do you find the LCM using the highlighted numbers?

• Divide the numbers

• Add the numbers

• Multiply the numbers

• Subtract the numbers

What is the LCM of 30 and 42?

• 60

• 42

• 210

• 120

Which column should you use to find the GCF?

• The column with 15 and 21

• The column with 2 and 3

• The column with 30 and 42

• The column with 5 and 7

What is the GCF of 30 and 42?

• 4

• 6

• 8

• 12