What is the GCF of 18 and 21?
Answer: The GCF or HCF of 18 and 21 is 3
The common methods of finding the GCF are prime factorization, listing the common factors. Let us see the methods in detail.
Methods to find GCF of 18 and 21
We can calculate the greatest common factor(GCF), by the following methods
Calculate GCF(18,21) by Prime Factorization
Let us represent 18 and 21 as a product of its prime numbers
2 × 3 × 3 is the prime factorization of 18
3 × 7 is the prime factorization of 21
Common factors = 3
The HCF or GCF is the product of the factors that are common to each of the given numbers.
So, the GCF is 3
Calculate GCF(18,21) by Listing the Common Factors
Common Factors of 18 and 21: 3
The greatest common factor is 3
The greatest common factor(GCF) or the highest common factor(HCF) of 18 and 21 is 3.