Common Denominator

The Common Denominator is the term used if the denominator of two or more fractions is the same.  Being able to calculate this is essential to adding fractions , subtracting fractions and comparing and ordering fractions.

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There are two methods to finding a Common Denominator

Method 1: Using Factors

Find the lowest common multiple of the two denominators. 

Change each of the fractions making their denominators the lowest common denominator and changing the numerator accordingly, producing   equivalent fractions

Add or Subtract your fractions as your math problem dictates. 

This seems to be a lot to remember, so I hear you asking if there isn't an easier 'standard' that you could remember.  The answer is YES - let's  move on to the next method.

Method 2: Multiplication Method

I will explain this using an example of two fractions:

Find the common denominator to add these two fractions

Multiply the Numerator and Denominator of fraction 1 by the denominator of fraction 2

Multiply the Numerator and Denominator of fraction 2 by the denominator of fraction 1

By doing this, we have created two new fractions, each equivalent to their originals, but now have the same denominator, which means we can now add or subtract with ease.


You can get plenty of common denominator calculating practice by using our comparing fractions worksheets   or select something different from our printable fraction worksheets section.

Feel free to explore everything else Printable Math Worksheets has to offer.

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