The HCF of 15 and 20 is 5. The greatest number that divides 15 and 20 perfectly without leaving any residue is the HCF of 15 and 20. The factors of 15 and 20 are 1, 3, 5, 15 and 1, 2, 4, 5, 10, 20, respectively. The long division, listing common factors, and prime factorisation are the three most prevalent methods for calculating the HCF of 15 and 20.
Also read: Highest common factor
What is the HCF of 15 and 20?
The answer to this question is 5. This article shows the HCF of 15 and 20 using various methods for your reference. The greatest of all their common factors is the Highest Common Factor (HCF) of two or more numbers.
How to Find HCF of 15 and 20?
There are three methods to find the HCF of 15 and 20:
- Prime Factorisation
- Long Division method
- Listing common factors
HCF of 15 and 20 by Prime Factorisation Method
The prime factorisation of 15 and 20 is given by:
Prime factorisation of 15 = (3 × 5)
Prime factorisation of 20 = (2 × 2 × 5)
The only common prime factor of 15 and 20 is 5.
Hence, HCF (15, 20) = 5
HCF of 15 and 20 by Long Division Method
The divisor that we receive when the remainder becomes 0 after executing long division repeatedly is the HCF of 15 and 20.
No further division can be done.
Hence, HCF (15, 20) = 5
HCF of 15 and 20 by Listing Common Factors
To calculate the HCF of 15 and 20 by listing out the common factors, list the factors as shown below.
Factors of 15: 1, 3, 5, 15
Factors of 20: 1, 2, 4, 5, 20
There are 2 common factors of 15 and 20; they are 1 and 5.
Therefore, the highest common factor of 15 and 20 is 5.
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HCF of 15 and 20 Solved Example
Question: Find the highest number that divides 15 and 20 exactly.
Solution:
The highest number that divides 15 and 20 exactly is their highest common factor, i.e. HCF of 15 and 20.
⇒ Factors of numbers 15 and 20:
Factors of 15 = 1, 3, 5, 15
Factors of 20 = 1, 2, 4, 5, 10, 20
Therefore, the HCF of 15 and 20 is 5.
Frequently Asked Questions on HCF of 15 and 20
What is the HCF of 15 and 20?
How to find the HCF of 15 and 20 by Prime Factorisation?
⇒ Since 5 is the only common prime factor of 15 and 20, HCF (15, 20) = 5.
What are the methods to find HCF of 15 and 20?
By Long Division
By Listing Common Factors
By Prime Factorisation
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