Least Common Multiple  of 3 and 7 is 21

How to find the Least Common Multiple of 3 and 7?

On this page below, we'll use the Prime Factorisation, and the List of Multiples method to find out the LCM of 3 and 7.

Follow the steps below, and let's calculate the LCM of 3 and 7.


Method 1 - Prime factorization

Step 1: Create a list of all the prime factors of the numbers 3 and 7:

Prime factors of 3

The prime factors of 3 are 3. Prime factorization of 3 in exponential form is:

3 = 31

Prime factors of 7

The prime factors of 7 are 7. Prime factorization of 7 in exponential form is:

7 = 71


Step 2: Identify the highest power of each prime number from the above boxes:

31, 71


Step 3: Multiply these values together:

31x71=21


Step 4: The result:

As seen on the calculation above, we have now obtained the LCM of 3 and 7.

The Least Common Multiple of 3 and 7 is 21.


Method 2 - List of Multiples

Find and list multiples of each number until the first common multiple is found. This is the lowest common multiple.


Multiples of 3:

3, 6, 9, 12, 15, 18, 21, 24, 27, 30

Multiples of 7:

7, 14, 21, 28, 35, 42


Therefore,

LCM(3, 7) = 21