To learn the relation between H.C.F. and L.C.M. of two numbers or the given n numbers first we need to know about the definition of the Highest Common Factor (H.C.F.) and the Least Common Multiple (L.C.M) and also LCM and HCF formulas. In this article, we are going to discuss the definition and the relation between HCF and LCM of given numbers in detail with examples.
Least Common Multiple(L.C.M)
The Least Common Multiple (LCM) is defined as the smallest number that is a multiple of all the numbers from a group of numbers.
Consider an example, the LCM of 12 and 15 is 60.
To find the LCM of numbers, first, mention the multiples of each number.
Therefore, the multiples of 12 = 12, 24, 36, 48, 60, 72, 84.. etc.,
The multiples of 15 = 15, 30, 45, 60, 75, 90, 105,.. Etc,
So, 60 is the smallest number that is a multiple of both 12 and 15
Highest Common Factor(H.C.F)
The Highest Common Factor ( HCF) is defined as the largest number that divides evenly into all the numbers from a group of numbers.
For example, the HCF of 12 and 15 is 3. Because 3 is the only common factor for both the numbers 12 and 15 and it is the largest number that divides both the numbers.
Prime factorisation of 12 = 2 x 2 x 3
Prime factorisation of 15 = 3 x 5
HCF and LCM Relation
The followings are the relation between HCF and LCM. Go through the relation between HCF and LCM, and solve the problem using the relations in an easy way.
(i) The product of LCM and HCF of the given natural numbers is equivalent to the product of the given numbers.
From the given property, LCM × HCF of a number = Product of the Numbers
Consider two numbers A and B, then.
Therefore,LCM (A , B) × HCF (A , B) = A × B
Example 1: Show that the LCM (6, 15) × HCF (6, 15) = Product(6, 15)
Solution: LCM and HCF of 6 and 15:
6 = 2 × 3
15 = 3 x 5
LCM of 6 and 15 = 30
HCF of 6 and 15 = 3
LCM (6, 15) × HCF (6, 15) = 30 × 3 = 90
Product of 6 and 15 = 6 × 15 = 90
Hence, LCM (6, 15) × HCF (6, 15)=Product(6, 15) = 90
(ii) The LCM of given co-prime numbers is equal to the product of the numbers since the HCF of co-prime numbers is 1.
So, LCM of Co-prime Numbers = Product Of The Numbers
Example 2: 17 and 23 are two co-prime numbers. By using the given numbers verify that,
LCM of given co-prime Numbers = Product of the given Numbers
Solution: LCM and HCF of 17 and 23:
17 = 1 x 7
23 = 1 x 23
LCM of 17 and 23 = 391
HCF of 17 and 23 = 1
Product of 17 and 23 = 17 × 23 = 391
Hence, LCM of co-prime numbers = Product of the numbers
(iii) H.C.F. and L.C.M. of Fractions
LCM of fractions = LCM of Numerators / HCF of Denominators
HCF of fractions = HCF of Numerators / LCM of Denominators
Example 3: Find the LCM of the fractions 1 / 2 , 3 / 8, 3 / 4
Solution:
LCM of fractions = LCM of Numerators/HCF of Denominators
LCM of fractions = LCM (1,3,3)/HCF(2,8,4)=3/2
Example 4: Find the HCF of the fractions 3 / 5, 6 / 11, 9 / 20
HCF of fractions HCF of Numerators/LCM of Denominators
HCF of fractions = HCF (3,6,9)/LCM (5,11,20)=3/220
For more information on the relation between HCF and LCM, download BYJU’S – The Learning App and also watch interactive videos to learn with ease.
| Related Links | |
| Composite Numbers | Odd Numbers |
| Co – Prime Numbers | Factors And Multiples |
Frequently Asked Questions on Relation Between HCF and LCM
What is the HCF of 5 and 15?
HCF(5, 15) = 5
Because
Factors of 5 are 1 and 5
Factors of 15 are 1, 3, 5 and 15
The highest common factor is 5.
What is the LCM of 5 and 15?
LCM (5, 15) = 15
Multiples of 5 are 5, 10, 15, 20, …
Multiples of 15 are 15, 30, ….
Hence, the least common multiple is 15.
If LCM and HCF of two numbers are 3 and 2 respectively, and one of the numbers is 6 then another number is?
We know that LCM × HCF = a × b where a, and b are two numbers
I.e., 3 × 2 = 6 × b
Therefore, b = 1.
What is the HCF of 2 and 4?
HCF(2, 4) = 2 because
Factors of 2 are 1 and 2
Factors of 4 are 1, 2 and 4
The highest common factor is 2.
What is the LCM of 2 and 4?
LCM(2, 4) = 4 because
Multiples of 2 are 2, 4, 6, 8, …
Multiples of 4 are 4, 8, ….
The least common multiple is 4.
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