# Common Denominator

## Common Denominator

Multiple of the denominators of two or more fractions.

The lowest common denominator for two or more fractions (LCM) is the lowest whole number that is also a multiple of each denominator in these fractions.

### Example

• Consider the fractions $$\frac{4}{12}$$ and $$\frac{8}{18}$$ : the numbers 36 and 72 could act as a common denominator, but the lowest option is 36, which we call the Lowest Common Multiple of 12 and 18 and that we write as: LCM (12, 18) = 36.
• The common denominator of the fractions $$\frac{3}{10}$$, $$\frac{7}{15}$$ and $$\frac{11}{20}$$ is 60.
Therefore, we write: LCM (10, 15, 20) = 60.