Maths HCF Highest Common Factor
Highest Common Factor
The highest common factor (HCF) of two or more integers is the largest positive integer that is a factor of all of the integers. It is also known as the greatest common divisor (GCD).
Finding the HCF
There are a few different ways to find the HCF of two or more integers. One common method is to use the Euclidean algorithm. This algorithm works by repeatedly dividing the larger integer by the smaller integer and taking the remainder. The last nonzero remainder is the HCF.
For example, to find the HCF of 12 and 18, we would use the following steps:
 Divide 18 by 12 to get a quotient of 1 and a remainder of 6.
 Divide 12 by 6 to get a quotient of 2 and a remainder of 0.
The last nonzero remainder is 6, so the HCF of 12 and 18 is 6.
Applications of the HCF
The HCF has a number of applications in mathematics and computer science, including:
 Finding the simplest form of a fraction.
 Solving Diophantine equations.
 Finding the greatest common divisor of a set of integers.
 Finding the least common multiple of a set of integers.
The HCF is a fundamental concept in number theory and has a wide range of applications in mathematics and computer science. It is a powerful tool that can be used to solve a variety of problems.
How to Find Highest Common Factor?
The highest common factor (HCF) of two or more numbers is the largest positive integer that divides each of the numbers without leaving a remainder. It is also known as the greatest common divisor (GCD).
Finding HCF using Prime Factorization
One way to find the HCF of two numbers is to use prime factorization. This involves expressing each number as a product of its prime factors, and then identifying the common prime factors. The HCF is the product of the common prime factors.
For example, let’s find the HCF of 12 and 18.
12 = 2 x 2 x 3 18 = 2 x 3 x 3
The common prime factors are 2 and 3. Therefore, the HCF of 12 and 18 is 2 x 3 = 6.
Finding HCF using the Euclidean Algorithm
Another way to find the HCF of two numbers is to use the Euclidean algorithm. This algorithm involves repeatedly dividing the larger number by the smaller number, and then taking the remainder. The HCF is the last nonzero remainder.
For example, let’s find the HCF of 12 and 18 using the Euclidean algorithm.
18 ÷ 12 = 1 remainder 6 12 ÷ 6 = 2 remainder 0
The last nonzero remainder is 6. Therefore, the HCF of 12 and 18 is 6.
Finding HCF using Online Calculators
There are also a number of online calculators that can be used to find the HCF of two or more numbers. These calculators are typically very easy to use, and they can provide the HCF in a matter of seconds.
The HCF of two or more numbers is a useful concept that can be used in a variety of applications. There are a number of different ways to find the HCF, and the best method will depend on the specific numbers involved.
HCF By Prime Factor Method
The prime factorization method is a systematic approach to finding the highest common factor (HCF) of two or more numbers. It involves expressing each number as a product of its prime factors and then identifying the common prime factors. The HCF is the product of these common prime factors.
Steps to Find HCF by Prime Factor Method:
 Prime Factorization: Express each given number as a product of its prime factors.
 Identify Common Prime Factors: Identify the common prime factors that appear in the prime factorizations of all the given numbers.
 Multiply Common Prime Factors: Multiply the common prime factors together to obtain the HCF.
Example:
Find the HCF of 12, 18, and 24 using the prime factor method.
Solution:

Prime Factorization:
 12 = 2 x 2 x 3
 18 = 2 x 3 x 3
 24 = 2 x 2 x 2 x 3

Identify Common Prime Factors:
 The common prime factors are 2 and 3.

Multiply Common Prime Factors:
 HCF = 2 x 3 = 6
Therefore, the HCF of 12, 18, and 24 is 6.
Advantages of Prime Factor Method:
 The prime factor method is a systematic and straightforward approach to finding the HCF.
 It provides a clear understanding of the factors involved in the HCF calculation.
 It can be easily applied to find the HCF of any number of positive integers.
The prime factor method is a reliable and efficient technique for determining the highest common factor of two or more numbers. By expressing the numbers as products of their prime factors and identifying the common factors, the HCF can be easily calculated. This method is particularly useful when dealing with large numbers or when the prime factorization of the numbers is known.
HCF By Division Method
The HCF (Highest Common Factor) or GCD (Greatest Common Divisor) of two or more numbers is the largest positive integer that divides each of the given numbers without leaving a remainder.
The division method is an efficient algorithm for finding the HCF of two or more numbers. It is based on the principle that the HCF of two numbers is the same as the HCF of their remainders when the larger number is divided by the smaller number.
Steps to Find HCF by Division Method:
 Arrange the numbers in descending order.
 Divide the larger number by the smaller number.
 If the remainder is zero, the smaller number is the HCF.
 If the remainder is not zero, repeat steps 2 and 3 with the smaller number and the remainder.
 Continue until the remainder is zero.
 The last nonzero remainder is the HCF of the given numbers.
Example:
Find the HCF of 12, 18, and 24 using the division method.
Solution:
 Arrange the numbers in descending order: 24, 18, 12.
 Divide the larger number (24) by the smaller number (12): 24 ÷ 12 = 2 with a remainder of 0.
 Since the remainder is zero, 12 is the HCF of 24, 18, and 12.
Advantages of Division Method:
 The division method is a simple and straightforward algorithm that can be easily understood and implemented.
 It is efficient and requires fewer steps compared to other methods like the prime factorization method.
 It can be used to find the HCF of any number of integers.
Disadvantages of Division Method:
 The division method can be timeconsuming for large numbers as it involves repeated division operations.
 It may not be suitable for finding the HCF of very large numbers as it requires precise division calculations.
In conclusion, the division method is a useful algorithm for finding the HCF of two or more numbers. It is simple, efficient, and can be applied to any number of integers. However, it may not be the most efficient method for finding the HCF of very large numbers.
HCF By Listing Factors Method
The HCF (Highest Common Factor) of two or more numbers is the largest number that divides each of the given numbers without leaving a remainder.
The listing factors method is a simple way to find the HCF of two numbers. To use this method, follow these steps:
 List all the factors of each number.
 Identify the common factors of the two numbers.
 The largest common factor is the HCF of the two numbers.
Example:
Find the HCF of 12 and 18.
Solution:
 The factors of 12 are 1, 2, 3, 4, 6, and 12.
 The factors of 18 are 1, 2, 3, 6, 9, and 18.
 The common factors of 12 and 18 are 1, 2, 3, and 6.
 The largest common factor of 12 and 18 is 6.
Note:
The HCF of two numbers can be found using other methods as well, such as the prime factorization method and the Euclidean algorithm. However, the listing factors method is a simple and straightforward method that can be used to find the HCF of two numbers quickly and easily.
HCF Formula
The Highest Common Factor (HCF) of two or more numbers is the largest positive integer that divides each of the numbers without leaving a remainder. It is also known as the Greatest Common Divisor (GCD).
Formula for Finding HCF
The HCF of two numbers, a and b, can be found using the following formula:
$$HCF(a, b) = gcd(a, b)$$
where gcd is the greatest common divisor function.
Example
To find the HCF of 12 and 18, we can use the following steps:
 List the factors of 12: 1, 2, 3, 4, 6, 12
 List the factors of 18: 1, 2, 3, 6, 9, 18
 Identify the common factors of 12 and 18: 1, 2, 3, 6
 The HCF of 12 and 18 is the largest of the common factors, which is 6.
The HCF of two numbers is a fundamental concept in mathematics with various applications. It can be found using the formula HCF(a, b) = gcd(a, b), where gcd is the greatest common divisor function. The HCF of two numbers has several properties, including being a positive integer, a divisor of both numbers, and the largest number that divides both numbers without leaving a remainder.
HCF of Multiple Numbers
The HCF (Highest Common Factor) of two or more numbers is the largest positive integer that divides each of the numbers without leaving a remainder. It is also known as the Greatest Common Divisor (GCD).
Finding the HCF of Two Numbers
To find the HCF of two numbers, you can use the following steps:
 List the factors of each number.
 Identify the common factors of the two numbers.
 The largest common factor is the HCF.
For example, to find the HCF of 12 and 18, we can list the factors of each number:
 Factors of 12: 1, 2, 3, 4, 6, 12
 Factors of 18: 1, 2, 3, 6, 9, 18
The common factors of 12 and 18 are 1, 2, 3, and 6. The largest common factor is 6, so the HCF of 12 and 18 is 6.
Finding the HCF of Multiple Numbers
To find the HCF of multiple numbers, you can use the following steps:
 Find the HCF of two of the numbers.
 Find the HCF of the result from step 1 and the third number.
 Repeat step 2 until you have found the HCF of all the numbers.
For example, to find the HCF of 12, 18, and 24, we can follow these steps:
 Find the HCF of 12 and 18: The HCF of 12 and 18 is 6.
 Find the HCF of 6 and 24: The HCF of 6 and 24 is 6.
Therefore, the HCF of 12, 18, and 24 is 6.
HCF of Prime Numbers
The highest common factor (HCF) of two or more numbers is the largest positive integer that divides each of the numbers without leaving a remainder.
HCF of Two Prime Numbers
The HCF of two prime numbers is always 1. This is because prime numbers are only divisible by themselves and 1.
HCF of Three or More Prime Numbers
The HCF of three or more prime numbers is always 1. This can be proven by using the fact that the HCF of two prime numbers is always 1.
Examples
 The HCF of 2 and 3 is 1.
 The HCF of 5 and 7 is 1.
 The HCF of 2, 3, and 5 is 1.
Conclusion
The HCF of prime numbers is a fundamental concept in number theory with a variety of applications.
Difference between HCF and LCM
HCF (Highest Common Factor)
 The HCF of two or more numbers is the largest number that divides each of the given numbers without leaving a remainder.
 It is also known as the greatest common divisor (GCD).
 The HCF of two numbers can be found by using the prime factorization method or the Euclidean algorithm.
LCM (Least Common Multiple)
 The LCM of two or more numbers is the smallest number that is divisible by each of the given numbers.
 It is also known as the lowest common multiple.
 The LCM of two numbers can be found by using the prime factorization method or the Euclidean algorithm.
Key Differences between HCF and LCM
Feature  HCF  LCM 

Definition  Largest number that divides each of the given numbers without leaving a remainder  Smallest number that is divisible by each of the given numbers 
Also known as  Greatest common divisor (GCD)  Lowest common multiple 
Method to find  Prime factorization method or Euclidean algorithm  Prime factorization method or Euclidean algorithm 
Relationship  The HCF and LCM of two numbers are related by the formula: HCF × LCM = Product of the two numbers 
Examples
 Find the HCF and LCM of 12 and 18.
Solution:

Prime factorization of 12: 2 × 2 × 3

Prime factorization of 18: 2 × 3 × 3

HCF of 12 and 18 = 6 (2 × 3)

LCM of 12 and 18 = 36 (2 × 2 × 3 × 3)

Find the HCF and LCM of 10, 15, and 20.
Solution:
 Prime factorization of 10: 2 × 5
 Prime factorization of 15: 3 × 5
 Prime factorization of 20: 2 × 2 × 5
 HCF of 10, 15, and 20 = 5
 LCM of 10, 15, and 20 = 60 (2 × 2 × 3 × 5)
Properties of HCF
The HCF of two or more integers has several important properties, which are listed below:
 Commutative property: The HCF of two integers a and b is the same as the HCF of b and a. In other words, $$HCF(a, b) = HCF(b, a).$$
 Associative property: The HCF of three or more integers is the same regardless of the order in which they are grouped. In other words, $$HCF(a, b, c) = HCF(a, HCF(b, c)) = HCF(HCF(a, b), c).$$
 Distributive property: The HCF of a product of two or more integers is equal to the product of the HCFs of the individual integers. In other words, $$HCF(a * b, c) = HCF(a, c) * HCF(b, c).$$
 Identity property: The HCF of an integer and itself is the integer itself. In other words, $$HCF(a, a) = a.$$
 Zero property: The HCF of an integer and zero is the integer itself. In other words, $$HCF(a, 0) = a.$$
 Coprime property: Two integers are said to be coprime if their HCF is 1. In other words, two integers a and b are coprime if $$HCF(a, b) = 1.$$
HCF (Highest Common Factor) FAQs
1. What is the HCF of two numbers?
The HCF (Highest Common Factor) of two numbers is the largest positive integer that divides both numbers without leaving a remainder.
2. How do you find the HCF of two numbers?
There are several methods to find the HCF of two numbers. One common method is the Euclidean algorithm, which involves repeatedly dividing the larger number by the smaller number and taking the remainder. The last nonzero remainder is the HCF.
3. What is the HCF of two coprime numbers?
Two coprime numbers are numbers that have no common factors other than 1. The HCF of two coprime numbers is 1.
4. What is the HCF of a number and 0?
The HCF of a number and 0 is the number itself.
5. What is the HCF of a number and 1?
The HCF of a number and 1 is 1.
6. What is the HCF of a number and itself?
The HCF of a number and itself is the number itself.
7. What is the HCF of a number and its negative?
The HCF of a number and its negative is the absolute value of the number.
8. What is the HCF of a number and its reciprocal?
The HCF of a number and its reciprocal is 1.
9. What is the HCF of a number and its square root?
The HCF of a number and its square root is either the square root or 1.
10. What is the HCF of a number and its cube root?
The HCF of a number and its cube root is either the cube root or 1.