Solution: The GCF of 140 and 70 is 70
Methods
How to find the GCF of 140 and 70 using Prime Factorization
One way to find the GCF of 140 and 70 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 140?
What are the Factors of 70?
Here is the prime factorization of 140:
2
2
×
5
1
×
7
1
2^2 × 5^1 × 7^1
2 2 × 5 1 × 7 1
And this is the prime factorization of 70:
2
1
×
5
1
×
7
1
2^1 × 5^1 × 7^1
2 1 × 5 1 × 7 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 140 and 70 by multiplying all the matching prime factors to get a GCF of 140 and 70 as 4900:
Thus, the GCF of 140 and 70 is: 4900
How to Find the GCF of 140 and 70 by Listing All Common Factors
The first step to this method of finding the Greatest Common Factor of 140 and 70 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, 140 and 70:
Factors of 140: 1, 2, 4, 5, 7, 10, 14, 20, 28, 35, 70, 140
Factors of 70: 1, 2, 5, 7, 10, 14, 35, 70
When you compare the two lists of factors, you can see that the common factor(s) are 1, 2, 5, 7, 10, 14, 35, 70. Since 70 is the largest of these common factors, the GCF of 140 and 70 would be 70.
Find the GCF of Other Number Pairs
Want more practice? Try some of these other GCF problems:
What is the GCF of 22 and 109?
What is the GCF of 119 and 29?
What is the GCF of 95 and 123?
What is the GCF of 143 and 88?
What is the GCF of 90 and 1?