LCM: (Least Common Multiple) 

The two most common methods of finding the LCM of two numbers are the Listing method and the Prime Factorization method.
The Listing Method: List the multiples of the larger number until you find a common product that is divisible by the smaller number. Example: To find the least common multiple of 6 and 8:
The Prime Factorization Method: This method is most useful if the numbers that you are trying to determine their LCM is very large.
Example: Find the LCM of 36 and 90: Step 1: Find the prime factorization of both numbers:
Step 2: List all the base numbers of the factors. As you see from above, you have a 2, 3, and a 5. Take the largest exponential value of all these numbers and multiply them. Look you have 2^{2} and 2 – take the 2^{2}. (only once) Next you have 3^{2} – take the 3^{2 } (only once) Next you have a 5 – take the 5 Multiply all the values that you have taken: 2 ^{2}· 3^{2} · 5 = 4 · 9 · 5 = 45 · 5 = 180 so the LCM is 180
