Worksheet showing how to use the ladder method to find GCF and LCM of given number pairs.

I'll solve each problem using the ladder method to find GCF and LCM.

Let me work through each pair step by step:

Problem 1: 12, 20

Finding GCF and LCM using ladder method:
- Start with 12 and 20
- Divide by 2: 12÷2=6, 20÷2=10
- Divide by 2 again: 6÷2=3, 10÷2=5
- Can't divide both by any common factor anymore (3 and 5 have no common factors)

GCF = 2 × 2 = 4
LCM = 2 × 2 × 3 × 5 = 60

Problem 2: 42, 28

Finding GCF and LCM using ladder method:
- Start with 42 and 28
- Divide by 2: 42÷2=21, 28÷2=14
- Divide by 7: 21÷7=3, 14÷7=2
- Can't divide both by any common factor anymore (3 and 2 have no common factors)

GCF = 2 × 7 = 14
LCM = 2 × 7 × 3 × 2 = 84

Problem 3: 26, 78

Finding GCF and LCM using ladder method:
- Start with 26 and 78
- Divide by 2: 26÷2=13, 78÷2=39
- Divide by 13: 13÷13=1, 39÷13=3
- Can't divide both by any common factor anymore (1 and 3 have no common factors)

GCF = 2 × 13 = 26
LCM = 2 × 13 × 1 × 3 = 78

Problem 4: 20, 130

Finding GCF and LCM using ladder method:
- Start with 20 and 130
- Divide by 2: 20÷2=10, 130÷2=65
- Divide by 5: 10÷5=2, 65÷5=13
- Can't divide both by any common factor anymore (2 and 13 have no common factors)

GCF = 2 × 5 = 10
LCM = 2 × 5 × 2 × 13 = 260

Final Answer:
12, 20: GCF = 4, LCM = 60
42, 28: GCF = 14, LCM = 84
26, 78: GCF = 26, LCM = 78
20, 130: GCF = 10, LCM = 260