Lowest Common Denominator

The Lowest Common Denominator is the smallest number that can be a denominator for two separate fractions. Another way to think of it is that it’s the smallest number that both original denominators can factor into. This is why the most common way to find the LCD is simply to multiply the two denominators together. For example:

1/2 + 4.5 

2  • 5 = 10 That makes 10 the lowest common denominator.

To get both fractions to that form, multiply them by the opposite denominator divided by itself. In the above example, that means multiply 1/2 by 5/5.

Since anything divided by itself = 1, that means the fraction is not being changed, only scaled.

The above equation thus becomes: 

5/10 + 8/10 = 13/10