When you are adding or subtracting fractions.
Because to add or subtract two fractions you first have to find equivalent fractions for both which have the same denominator.
A common denominator is needed when adding or subtracting fractions of different denominators.
If you are adding or subtracting unlike fractions, convert them to equivalent fractions with a common denominator.
What is the definition of Adding and Subtracting Like Fractions
Subtracting a fraction is the same as adding its negative.
When adding or subtracting fractions their denominators must be the same
Ensure that the denominators are the same when adding or subtracting fractions.
Before adding or subtracting two fractions they are converted into like fractions. Explain with examples why this is necessary.
A Common Denominator
You need a common denominator for both.
They have to have the same denominator.
I learned to always change the denominators before adding or subtracting the numerators. You must always have a common denominator before adding or subtracting.
Find a common denamonator.