LCM of 4 and 20
LCM of 4 and 20 is the smallest number among all common multiples of 4 and 20. The first few multiples of 4 and 20 are (4, 8, 12, 16, 20, . . . ) and (20, 40, 60, 80, 100, 120, . . . ) respectively. There are 3 commonly used methods to find LCM of 4 and 20  by division method, by prime factorization, and by listing multiples.
1.  LCM of 4 and 20 
2.  List of Methods 
3.  Solved Examples 
4.  FAQs 
What is the LCM of 4 and 20?
Answer: LCM of 4 and 20 is 20.
Explanation:
The LCM of two nonzero integers, x(4) and y(20), is the smallest positive integer m(20) that is divisible by both x(4) and y(20) without any remainder.
Methods to Find LCM of 4 and 20
The methods to find the LCM of 4 and 20 are explained below.
 By Listing Multiples
 By Division Method
 By Prime Factorization Method
LCM of 4 and 20 by Listing Multiples
To calculate the LCM of 4 and 20 by listing out the common multiples, we can follow the given below steps:
 Step 1: List a few multiples of 4 (4, 8, 12, 16, 20, . . . ) and 20 (20, 40, 60, 80, 100, 120, . . . . )
 Step 2: The common multiples from the multiples of 4 and 20 are 20, 40, . . .
 Step 3: The smallest common multiple of 4 and 20 is 20.
∴ The least common multiple of 4 and 20 = 20.
LCM of 4 and 20 by Division Method
To calculate the LCM of 4 and 20 by the division method, we will divide the numbers(4, 20) by their prime factors (preferably common). The product of these divisors gives the LCM of 4 and 20.
 Step 1: Find the smallest prime number that is a factor of at least one of the numbers, 4 and 20. Write this prime number(2) on the left of the given numbers(4 and 20), separated as per the ladder arrangement.
 Step 2: If any of the given numbers (4, 20) is a multiple of 2, divide it by 2 and write the quotient below it. Bring down any number that is not divisible by the prime number.
 Step 3: Continue the steps until only 1s are left in the last row.
The LCM of 4 and 20 is the product of all prime numbers on the left, i.e. LCM(4, 20) by division method = 2 × 2 × 5 = 20.
LCM of 4 and 20 by Prime Factorization
Prime factorization of 4 and 20 is (2 × 2) = 2^{2} and (2 × 2 × 5) = 2^{2} × 5^{1} respectively. LCM of 4 and 20 can be obtained by multiplying prime factors raised to their respective highest power, i.e. 2^{2} × 5^{1} = 20.
Hence, the LCM of 4 and 20 by prime factorization is 20.
☛ Also Check:
 LCM of 96 and 404  9696
 LCM of 60 and 700  2100
 LCM of 6 and 16  48
 LCM of 36, 42 and 72  504
 LCM of 28 and 32  224
 LCM of 6, 7 and 9  126
 LCM of 4, 12 and 20  60
LCM of 4 and 20 Examples

Example 1: The product of two numbers is 80. If their GCD is 4, what is their LCM?
Solution:
Given: GCD = 4
product of numbers = 80
∵ LCM × GCD = product of numbers
⇒ LCM = Product/GCD = 80/4
Therefore, the LCM is 20.
The probable combination for the given case is LCM(4, 20) = 20. 
Example 2: Verify the relationship between GCF and LCM of 4 and 20.
Solution:
The relation between GCF and LCM of 4 and 20 is given as,
LCM(4, 20) × GCF(4, 20) = Product of 4, 20
Prime factorization of 4 and 20 is given as, 4 = (2 × 2) = 2^{2} and 20 = (2 × 2 × 5) = 2^{2} × 5^{1}
LCM(4, 20) = 20
GCF(4, 20) = 4
LHS = LCM(4, 20) × GCF(4, 20) = 20 × 4 = 80
RHS = Product of 4, 20 = 4 × 20 = 80
⇒ LHS = RHS = 80
Hence, verified. 
Example 3: The GCD and LCM of two numbers are 4 and 20 respectively. If one number is 20, find the other number.
Solution:
Let the other number be m.
∵ GCD × LCM = 20 × m
⇒ m = (GCD × LCM)/20
⇒ m = (4 × 20)/20
⇒ m = 4
Therefore, the other number is 4.
FAQs on LCM of 4 and 20
What is the LCM of 4 and 20?
The LCM of 4 and 20 is 20. To find the least common multiple (LCM) of 4 and 20, we need to find the multiples of 4 and 20 (multiples of 4 = 4, 8, 12, 16 . . . . 20; multiples of 20 = 20, 40, 60, 80) and choose the smallest multiple that is exactly divisible by 4 and 20, i.e., 20.
If the LCM of 20 and 4 is 20, Find its GCF.
LCM(20, 4) × GCF(20, 4) = 20 × 4
Since the LCM of 20 and 4 = 20
⇒ 20 × GCF(20, 4) = 80
Therefore, the greatest common factor = 80/20 = 4.
How to Find the LCM of 4 and 20 by Prime Factorization?
To find the LCM of 4 and 20 using prime factorization, we will find the prime factors, (4 = 2 × 2) and (20 = 2 × 2 × 5). LCM of 4 and 20 is the product of prime factors raised to their respective highest exponent among the numbers 4 and 20.
⇒ LCM of 4, 20 = 2^{2} × 5^{1} = 20.
What is the Least Perfect Square Divisible by 4 and 20?
The least number divisible by 4 and 20 = LCM(4, 20)
LCM of 4 and 20 = 2 × 2 × 5 [Incomplete pair(s): 5]
⇒ Least perfect square divisible by each 4 and 20 = LCM(4, 20) × 5 = 100 [Square root of 100 = √100 = ±10]
Therefore, 100 is the required number.
What are the Methods to Find LCM of 4 and 20?
The commonly used methods to find the LCM of 4 and 20 are:
 Division Method
 Listing Multiples
 Prime Factorization Method
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