Solution: The GCF of 102 and 45 is 3
Methods
How to find the GCF of 102 and 45 using Prime Factorization
One way to find the GCF of 102 and 45 is to compare the prime factorization of each number. To find the prime factorization, you can follow the instructions for each number here:
What are the Factors of 102?
What are the Factors of 45?
Here is the prime factorization of 102:
2
1
×
3
1
×
1
7
1
2^1 × 3^1 × 17^1
2 1 × 3 1 × 1 7 1
And this is the prime factorization of 45:
3
2
×
5
1
3^2 × 5^1
3 2 × 5 1
When you compare the prime factorization of these two numbers, you can see that there are matching prime factors. You can now find the Greatest Common Factor of 102 and 45 by multiplying all the matching prime factors to get a GCF of 102 and 45 as 9:
Thus, the GCF of 102 and 45 is: 9
How to Find the GCF of 102 and 45 by Listing All Common Factors
The first step to this method of finding the Greatest Common Factor of 102 and 45 is to find and list all the factors of each number. Again, you can see how this is done by looking at the “Factors of” articles that are linked to above.
Let’s take a look at the factors for each of these numbers, 102 and 45:
Factors of 102: 1, 2, 3, 6, 17, 34, 51, 102
Factors of 45: 1, 3, 5, 9, 15, 45
When you compare the two lists of factors, you can see that the common factor(s) are 1, 3. Since 3 is the largest of these common factors, the GCF of 102 and 45 would be 3.
Find the GCF of Other Number Pairs
Want more practice? Try some of these other GCF problems:
What is the GCF of 40 and 29?
What is the GCF of 135 and 112?
What is the GCF of 86 and 94?
What is the GCF of 123 and 144?
What is the GCF of 98 and 80?