The Least Common Multiple of two or more rational numbers is the smallest positive rational number which is a multiple of all the given rational numbers.

For example, let us find the LCM of 2 and 6.
Multiples of 2 are 2, 4, 6, 8, 10, 12.....
Multiples of 6 are 6, 12, 18, 24, 30....

From the numbers listed above, we can easily find out that 6 is the least common multiple of 2 and 6.

LCM can be defined as the smallest of the common multiples. Also, a common multiple of two numbers that is exactly divisible by each number. Hence, we can define the least common multiple(LCM) of two numbers as the smallest number, which is not equal to zero, which is a multiple of both.

Let us consider the multiples of some numbers. The multiple of a number can be taken as those numbers obtained by multiplying it by other numbers.

Multiples of 4 are 4, 8, 12, and so on.
Multiples of 6 are 6, 12, 18 and so on.

From these two groups, it can be seen that, 12 is common to both or it can be said that 12 is a common multiple of 6 and 4. There are several common multiples of 6 and 4. They are 12, 24, 36 and so on. The least of the common multiples for the above two numbers is 12. Hence, 12 is the least common multiple of 6 and 4.