Least common denominator

The least common denominator (LCD) for two or more common fractions is the least common multiple of the denominators. There are several ways to find the least common denominator of two or more fractions. One way is by listing multiples

Examples

1. What is the least common denominator of and ?

Multiples of 4: 4, 8, 12, ...
Multiples of 6: 6, 12, ...

Thus, the least common denominator of and is 12.

2. What is the least common denominator of , , and ?

Multiples of 4: 4, 8, 12, 16, 20, ...
Multiples of 5: 5, 10, 15, 20, ...
Multiples of 2: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, ...

Thus, the least common denominator of , , and is 20.

This is written as LCD() = 20.


See also common multiple, least common multiple.