To find out the least common denominator of a set of numbers, you have to find out the least possible number which divides all the numbers in that set till the answers are divisible only by 1.

Let us take an example,

2,4,6

Now, all these numbers can be divided by 2.

After you divide them by 2, you get the answers as 1,2,3 respectively which can further not be divided by any common number except 1.

Hence, the least comon denominator of this set is 2.