The Least Common Denominator (LCD) is the smallest common denominator of two or more fractions.

Example: the LCD for 3/5, 1/6 and 1/15 is 30.

List the multiples of each denominator 5, 6 and 15

Multiples of 5 are 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60…..

Multiples of 6 are 12, 18, 24, 30, 36, 42, 48, 54, 60 ...

Multiples of 15 are 30, 45, 60…

30 is the smallest number that appears in each list.

Therefore, the least common denominator of 3/5, 1/6 and 1/15 is 30.