LCM of 12, 18, and 20
LCM of 12, 18, and 20 is the smallest number among all common multiples of 12, 18, and 20. The first few multiples of 12, 18, and 20 are (12, 24, 36, 48, 60 . . .), (18, 36, 54, 72, 90 . . .), and (20, 40, 60, 80, 100 . . .) respectively. There are 3 commonly used methods to find LCM of 12, 18, 20  by prime factorization, by division method, and by listing multiples.
1.  LCM of 12, 18, and 20 
2.  List of Methods 
3.  Solved Examples 
4.  FAQs 
What is the LCM of 12, 18, and 20?
Answer: LCM of 12, 18, and 20 is 180.
Explanation:
The LCM of three nonzero integers, a(12), b(18), and c(20), is the smallest positive integer m(180) that is divisible by a(12), b(18), and c(20) without any remainder.
Methods to Find LCM of 12, 18, and 20
Let's look at the different methods for finding the LCM of 12, 18, and 20.
 By Listing Multiples
 By Division Method
 By Prime Factorization Method
LCM of 12, 18, and 20 by Listing Multiples
To calculate the LCM of 12, 18, 20 by listing out the common multiples, we can follow the given below steps:
 Step 1: List a few multiples of 12 (12, 24, 36, 48, 60 . . .), 18 (18, 36, 54, 72, 90 . . .), and 20 (20, 40, 60, 80, 100 . . .).
 Step 2: The common multiples from the multiples of 12, 18, and 20 are 180, 360, . . .
 Step 3: The smallest common multiple of 12, 18, and 20 is 180.
∴ The least common multiple of 12, 18, and 20 = 180.
LCM of 12, 18, and 20 by Division Method
To calculate the LCM of 12, 18, and 20 by the division method, we will divide the numbers(12, 18, 20) by their prime factors (preferably common). The product of these divisors gives the LCM of 12, 18, and 20.
 Step 1: Find the smallest prime number that is a factor of at least one of the numbers, 12, 18, and 20. Write this prime number(2) on the left of the given numbers(12, 18, and 20), separated as per the ladder arrangement.
 Step 2: If any of the given numbers (12, 18, 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 12, 18, and 20 is the product of all prime numbers on the left, i.e. LCM(12, 18, 20) by division method = 2 × 2 × 3 × 3 × 5 = 180.
LCM of 12, 18, and 20 by Prime Factorization
Prime factorization of 12, 18, and 20 is (2 × 2 × 3) = 2^{2} × 3^{1}, (2 × 3 × 3) = 2^{1} × 3^{2}, and (2 × 2 × 5) = 2^{2} × 5^{1} respectively. LCM of 12, 18, and 20 can be obtained by multiplying prime factors raised to their respective highest power, i.e. 2^{2} × 3^{2} × 5^{1} = 180.
Hence, the LCM of 12, 18, and 20 by prime factorization is 180.
ā Also Check:
 LCM of 6 and 30  30
 LCM of 11 and 18  198
 LCM of 36 and 54  108
 LCM of 25 and 40  200
 LCM of 10 and 24  120
 LCM of 6 and 12  12
 LCM of 45 and 60  180
LCM of 12, 18, and 20 Examples

Example 1: Verify the relationship between the GCD and LCM of 12, 18, and 20.
Solution:
The relation between GCD and LCM of 12, 18, and 20 is given as,
LCM(12, 18, 20) = [(12 × 18 × 20) × GCD(12, 18, 20)]/[GCD(12, 18) × GCD(18, 20) × GCD(12, 20)]
⇒ Prime factorization of 12, 18 and 20: 12 = 2^{2} × 3^{1}
 18 = 2^{1} × 3^{2}
 20 = 2^{2} × 5^{1}
∴ GCD of (12, 18), (18, 20), (12, 20) and (12, 18, 20) = 6, 2, 4 and 2 respectively.
Now, LHS = LCM(12, 18, 20) = 180.
And, RHS = [(12 × 18 × 20) × GCD(12, 18, 20)]/[GCD(12, 18) × GCD(18, 20) × GCD(12, 20)] = [(4320) × 2]/[6 × 2 × 4] = 180
LHS = RHS = 180.
Hence verified. 
Example 2: Calculate the LCM of 12, 18, and 20 using the GCD of the given numbers.
Solution:
Prime factorization of 12, 18, 20:
 12 = 2^{2} × 3^{1}
 18 = 2^{1} × 3^{2}
 20 = 2^{2} × 5^{1}
Therefore, GCD(12, 18) = 6, GCD(18, 20) = 2, GCD(12, 20) = 4, GCD(12, 18, 20) = 2
We know,
LCM(12, 18, 20) = [(12 × 18 × 20) × GCD(12, 18, 20)]/[GCD(12, 18) × GCD(18, 20) × GCD(12, 20)]
LCM(12, 18, 20) = (4320 × 2)/(6 × 2 × 4) = 180
⇒LCM(12, 18, 20) = 180 
Example 3: Find the smallest number that is divisible by 12, 18, 20 exactly.
Solution:
The smallest number that is divisible by 12, 18, and 20 exactly is their LCM.
⇒ Multiples of 12, 18, and 20: Multiples of 12 = 12, 24, 36, 48, 60, 72, 84, 96, 108, 120, 132, 144, 156, 168, 180, . . . .
 Multiples of 18 = 18, 36, 54, 72, 90, 108, 126, 144, 162, 180, . . . .
 Multiples of 20 = 20, 40, 60, 80, 100, 120, 140, 160, 180, . . . .
Therefore, the LCM of 12, 18, and 20 is 180.
FAQs on LCM of 12, 18, and 20
What is the LCM of 12, 18, and 20?
The LCM of 12, 18, and 20 is 180. To find the least common multiple (LCM) of 12, 18, and 20, we need to find the multiples of 12, 18, and 20 (multiples of 12 = 12, 24, 36, 48 . . . . 180 . . . . ; multiples of 18 = 18, 36, 54, 72 . . . . 180 . . . . ; multiples of 20 = 20, 40, 60, 80 . . . . 180 . . . . ) and choose the smallest multiple that is exactly divisible by 12, 18, and 20, i.e., 180.
What are the Methods to Find LCM of 12, 18, 20?
The commonly used methods to find the LCM of 12, 18, 20 are:
 Listing Multiples
 Division Method
 Prime Factorization Method
How to Find the LCM of 12, 18, and 20 by Prime Factorization?
To find the LCM of 12, 18, and 20 using prime factorization, we will find the prime factors, (12 = 2^{2} × 3^{1}), (18 = 2^{1} × 3^{2}), and (20 = 2^{2} × 5^{1}). LCM of 12, 18, and 20 is the product of prime factors raised to their respective highest exponent among the numbers 12, 18, and 20.
⇒ LCM of 12, 18, 20 = 2^{2} × 3^{2} × 5^{1} = 180.
What is the Least Perfect Square Divisible by 12, 18, and 20?
The least number divisible by 12, 18, and 20 = LCM(12, 18, 20)
LCM of 12, 18, and 20 = 2 × 2 × 3 × 3 × 5 [Incomplete pair(s): 5]
⇒ Least perfect square divisible by each 12, 18, and 20 = LCM(12, 18, 20) × 5 = 900 [Square root of 900 = √900 = ±30]
Therefore, 900 is the required number.