GCF and LCM

The Ladder Method

• Step 1: Write your numbers side by side inside a letter L

» Ex.) 12 and 8

12 8

• Step 2: Find the smallest number that will go into both numbers evenly and put it on the left of the L

2 12 8

• Step 3: Divide the number to the left into both numbers and put the answers underneath. Repeat steps 2 and 3 until you can no longer divide.

2 12 8

6 4

• Step 4: Repeat steps 2 and 3 until you can no longer divide.

2 12 8

6 4

3 2

2

• Step 5: Multiply all the numbers on the left of the L’s to find the GCF. 2 X 2 = 4

• The GCF is 4

2 12 8

6 4

3 2

2

• Step 6: Multiply all the numbers on the left of the L’s and below the last L to find the LCM. 2 X 2 X 3 X 2 = 24

• The LCM is 24

2 12 8

6 4

3 2

2