The HCF of 18 and 20 is 2. HCF is the greatest integer that can divide 18 and 20 evenly, and that number is 2. HCF stands for Highest Common Factor. It is also known as GCF (Greatest Common Factor) or GCD (Greatest Common Divisor). For a given set of numbers, there would be multiple common factors, and the highest among the common factors is known as the HCF. For 18 and 20, the common factors are 1 and 2. Since 2 is the highest among the given factors, HCF would be 2 for 18 and 20. You can refer to GCF for more details.
What is the HCF 18 and 20?
The Highest Common Factor, also known as the Greatest Common Factor of 18 and 20, is 2.
How to Find HCF of 18 and 20?
There are three methods to find the HCF of 18 and 20:
- Prime Factorisation
- Long Division method
- Listing common factors
HCF of 18 and 20 by Prime Factorisation Method
In the prime factorisation method, the numbers can be expressed as the product of prime numbers. Here, 18 and 20 can be expressed as:
18 = 2 × 3 × 3
20 = 2 × 2 × 5
The common prime factor is 2.
Therefore HCF (18, 20) = 2
HCF of 18 and 20 by Long Division Method
In the long division method, the following steps are followed.
- From the given set of numbers, the smallest number becomes the divisor, and the larger number becomes the dividend.
- In the next step, the smaller number becomes the dividend, and the remainder becomes the divisor.
- The above step is followed until the remainder is zero.
- The last divisor would be the HCF.
The HCF of 18 and 20 by long division method is:
Therefore, HCF (18, 20) = 2
HCF of 18 and 20 by Listing Common Factors
By listing common factors of given numbers, we can identify the Highest/Greatest/Biggest Common Factor, which is the HCF. Below is the list of factors for 18 and 20:
Factors of 18: 1, 2, 3, 6, 9 and 18
Factors of 20: 1, 2, 4, 5, 10 and 20
Therefore, HCF (18, 20) = 2
Related Articles
Video Lesson on Properties of HCF and LCM
Solved Examples
1. Find the greatest number that divides 9 and 18.
Solution: The greatest number that divides both 9 and 18 is nothing but the GCF, which is 9.
2. What is the GCF of 70 and 77?
Solution: The GCF of 70 and 77 is 7.
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