How to find the Least Common Multiple of 15 and 21?
On this page below, we'll use the Prime Factorisation, and the List of Multiples method to find out the LCM of 15 and 21.
Follow the steps below, and let's calculate the LCM of 15 and 21.
Method 1 - Prime factorization
Step 1: Create a list of all the prime factors of the numbers 15 and 21:
Prime factors of 15
The prime factors of 15 are 3 and 5. Prime factorization of 15 in exponential form is:
15 = 31x51
Prime factors of 21
The prime factors of 21 are 3 and 7. Prime factorization of 21 in exponential form is:
21 = 31x71
Step 2: Identify the highest power of each prime number from the above boxes:
31, 51, 71
Step 3: Multiply these values together:
31x51x71=105
Step 4: The result:
As seen on the calculation above, we have now obtained the LCM of 15 and 21.
The Least Common Multiple of 15 and 21 is 105.
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 15:
15, 30, 45, 60, 75, 90, 105, 120, 135, 150
Multiples of 21:
21, 42, 63, 84, 105, 126, 147, 168
Therefore,
LCM(15, 21) = 105