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Greatest Common Divisor - GCD, Lecture notes of Mathematics

The Greatest Common Divisor (GCD) refers to the greatest number that is a common divisor for a given set of numbers. It is also termed as the Highest Common Factor (HCF) or the Greatest Common Factor (GCF). In this lesson, we will learn how to find the greatest common divisor in detail.

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2024/2025

Uploaded on 12/30/2024

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Greatest Common Divisor - GCD
The Greatest Common Divisor (GCD) refers to the greatest number that is a
common divisor for a given set of numbers. It is also termed as the Highest
Common Factor (HCF) or the Greatest Common Factor (GCF). In this lesson, we
will learn how to find the greatest common divisor in detail.
What is Greatest Common Divisor?
For a set of positive integers (a, b), the greatest common divisor is defined as the
greatest positive!number!which is a common factor of both the positive!integers!(a,
b). GCD of any two numbers is never negative or 0 as the least positive integer
common to any two numbers is always 1.
GCD Meaning - GCD Full Form
The meaning and full form of GCD is the Greatest Common Divisor. So, GCD is
the greatest positive number which is a common divisor for a given set of positive
numbers.
How to Find the Greatest Common Divisor?
For a set of two positive integers (a, b) we use the following steps to find the
greatest common divisor:
GCD of Two Numbers
Let us see the steps given below to learn how to find the GCD of two numbers.
Step 1:!Write the divisors of the number 'a'.
Step 2:!Write the divisors of the number 'b'.
Step 3:!List the common divisors of 'a' and 'b'.
Step 4:!Now find the divisor which is the highest among the common divisors.
Example:!Find the greatest common divisor of 13 and 48.
Solution:!We will use the following steps to find the greatest common divisor of
(13, 48).
Divisors of 13 = 1, and 13.
Divisors of 48 = 1, 2, 3, 4, 6, 8, 12, 16, 24 and 48.
The common divisor of 13 and 48 is 1.
The greatest common divisor of 13 and 48 is 1.
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Greatest Common Divisor - GCD

The Greatest Common Divisor (GCD) refers to the greatest number that is a common divisor for a given set of numbers. It is also termed as the Highest Common Factor (HCF) or the Greatest Common Factor (GCF). In this lesson, we will learn how to find the greatest common divisor in detail.

What is Greatest Common Divisor?

For a set of positive integers (a, b), the greatest common divisor is defined as the greatest positive number which is a common factor of both the positive integers (a, b). GCD of any two numbers is never negative or 0 as the least positive integer common to any two numbers is always 1.

GCD Meaning - GCD Full Form

The meaning and full form of GCD is the Greatest Common Divisor. So, GCD is the greatest positive number which is a common divisor for a given set of positive numbers.

How to Find the Greatest Common Divisor?

For a set of two positive integers (a, b) we use the following steps to find the greatest common divisor:

GCD of Two Numbers

Let us see the steps given below to learn how to find the GCD of two numbers.  Step 1: Write the divisors of the number 'a'.  Step 2: Write the divisors of the number 'b'.  Step 3: List the common divisors of 'a' and 'b'.  Step 4: Now find the divisor which is the highest among the common divisors. Example: Find the greatest common divisor of 13 and 48. Solution: We will use the following steps to find the greatest common divisor of (13, 48). Divisors of 13 = 1, and 13. Divisors of 48 = 1, 2, 3, 4, 6, 8, 12, 16, 24 and 48. The common divisor of 13 and 48 is 1. The greatest common divisor of 13 and 48 is 1.

Therefore, GCD (13, 48) = 1 Finding Greatest Common Divisor by LCM Method As per the LCM Method for the greatest common divisor, the GCD of two positive integers (a, b) can be calculated by using the following formula:

How to Calculate the GCD using LCM?

Let us see how to calculate the GCD of (a, b) using the LCM method:  Step 1: Find the product of a and b.  Step 2: Find the Least Common Multiple (LCM) of a and b.  Step 3: Divide the product of the numbers by the LCM of the numbers.  Step 4: The obtained value after division is the greatest common divisor of (a, b). Example: Find the greatest common divisor of 15 and 70 using the LCM method. Solution: The greatest common divisor of 15 and 70 can be calculated as follows:  The product of 15 and 70 is given as, 15 × 70  The LCM of (15, 70) is 210.  We know that GCD (a, b) = (a × b)/ LCM of a and b  GCD (15, 70) = (15 × 70)/ 210 = 5. ∴ The greatest common divisor of (15, 70) is 5. Example: Find the GCF of 64 and 112. Solution: Factors of 64: 1, 2, 4, 8, 16, 32, 64 Factors of 112: 1, 2, 4, 7, 8, 14, 16, 28, 56, 112 Common Factors: 1, 2, 4, 7, 8, 16 Greatest Common Factor: 16