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 [latex]\frac{4}{12}[/latex] and [latex]\frac{8}{18}[/latex] : 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 [latex]\frac{3}{10}[/latex], [latex]\frac{7}{15}[/latex] and [latex]\frac{11}{20}[/latex] is 60. Therefore, we write: LCM (10, 15, 20) = 60.