GCF of 100 and 120
GCF of 100 and 120 is the largest possible number that divides 100 and 120 exactly without any remainder. The factors of 100 and 120 are 1, 2, 4, 5, 10, 20, 25, 50, 100 and 1, 2, 3, 4, 5, 6, 8, 10, 12, 15, 20, 24, 30, 40, 60, 120 respectively. There are 3 commonly used methods to find the GCF of 100 and 120  prime factorization, long division, and Euclidean algorithm.
1.  GCF of 100 and 120 
2.  List of Methods 
3.  Solved Examples 
4.  FAQs 
What is GCF of 100 and 120?
Answer: GCF of 100 and 120 is 20.
Explanation:
The GCF of two nonzero integers, x(100) and y(120), is the greatest positive integer m(20) that divides both x(100) and y(120) without any remainder.
Methods to Find GCF of 100 and 120
The methods to find the GCF of 100 and 120 are explained below.
 Prime Factorization Method
 Using Euclid's Algorithm
 Long Division Method
GCF of 100 and 120 by Prime Factorization
Prime factorization of 100 and 120 is (2 × 2 × 5 × 5) and (2 × 2 × 2 × 3 × 5) respectively. As visible, 100 and 120 have common prime factors. Hence, the GCF of 100 and 120 is 2 × 2 × 5 = 20.
GCF of 100 and 120 by Euclidean Algorithm
As per the Euclidean Algorithm, GCF(X, Y) = GCF(Y, X mod Y)
where X > Y and mod is the modulo operator.
Here X = 120 and Y = 100
 GCF(120, 100) = GCF(100, 120 mod 100) = GCF(100, 20)
 GCF(100, 20) = GCF(20, 100 mod 20) = GCF(20, 0)
 GCF(20, 0) = 20 (∵ GCF(X, 0) = X, where X ≠ 0)
Therefore, the value of GCF of 100 and 120 is 20.
GCF of 100 and 120 by Long Division
GCF of 100 and 120 is the divisor that we get when the remainder becomes 0 after doing long division repeatedly.
 Step 1: Divide 120 (larger number) by 100 (smaller number).
 Step 2: Since the remainder ≠ 0, we will divide the divisor of step 1 (100) by the remainder (20).
 Step 3: Repeat this process until the remainder = 0.
The corresponding divisor (20) is the GCF of 100 and 120.
☛ Also Check:
 GCF of 24 and 72 = 24
 GCF of 15 and 18 = 3
 GCF of 18 and 20 = 2
 GCF of 15 and 27 = 3
 GCF of 8 and 24 = 8
 GCF of 56 and 84 = 28
 GCF of 12 and 32 = 4
GCF of 100 and 120 Examples

Example 1: The product of two numbers is 12000. If their GCF is 20, what is their LCM?
Solution:
Given: GCF = 20 and product of numbers = 12000
∵ LCM × GCF = product of numbers
⇒ LCM = Product/GCF = 12000/20
Therefore, the LCM is 600. 
Example 2: Find the greatest number that divides 100 and 120 exactly.
Solution:
The greatest number that divides 100 and 120 exactly is their greatest common factor, i.e. GCF of 100 and 120.
⇒ Factors of 100 and 120: Factors of 100 = 1, 2, 4, 5, 10, 20, 25, 50, 100
 Factors of 120 = 1, 2, 3, 4, 5, 6, 8, 10, 12, 15, 20, 24, 30, 40, 60, 120
Therefore, the GCF of 100 and 120 is 20.

Example 3: For two numbers, GCF = 20 and LCM = 600. If one number is 120, find the other number.
Solution:
Given: GCF (x, 120) = 20 and LCM (x, 120) = 600
∵ GCF × LCM = 120 × (x)
⇒ x = (GCF × LCM)/120
⇒ x = (20 × 600)/120
⇒ x = 100
Therefore, the other number is 100.
FAQs on GCF of 100 and 120
What is the GCF of 100 and 120?
The GCF of 100 and 120 is 20. To calculate the greatest common factor (GCF) of 100 and 120, we need to factor each number (factors of 100 = 1, 2, 4, 5, 10, 20, 25, 50, 100; factors of 120 = 1, 2, 3, 4, 5, 6, 8, 10, 12, 15, 20, 24, 30, 40, 60, 120) and choose the greatest factor that exactly divides both 100 and 120, i.e., 20.
How to Find the GCF of 100 and 120 by Prime Factorization?
To find the GCF of 100 and 120, we will find the prime factorization of the given numbers, i.e. 100 = 2 × 2 × 5 × 5; 120 = 2 × 2 × 2 × 3 × 5.
⇒ Since 2, 2, 5 are common terms in the prime factorization of 100 and 120. Hence, GCF(100, 120) = 2 × 2 × 5 = 20
☛ Prime Numbers
How to Find the GCF of 100 and 120 by Long Division Method?
To find the GCF of 100, 120 using long division method, 120 is divided by 100. The corresponding divisor (20) when remainder equals 0 is taken as GCF.
If the GCF of 120 and 100 is 20, Find its LCM.
GCF(120, 100) × LCM(120, 100) = 120 × 100
Since the GCF of 120 and 100 = 20
⇒ 20 × LCM(120, 100) = 12000
Therefore, LCM = 600
☛ GCF Calculator
What is the Relation Between LCM and GCF of 100, 120?
The following equation can be used to express the relation between LCM and GCF of 100 and 120, i.e. GCF × LCM = 100 × 120.
What are the Methods to Find GCF of 100 and 120?
There are three commonly used methods to find the GCF of 100 and 120.
 By Long Division
 By Euclidean Algorithm
 By Prime Factorization
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