Adding and Subtracting Fractions
1. Addition and Subtraction when the denominators are the same:
To add or subtract fractions that have the same denominator, add or
subtract the numerators to get the numerator of the answer and carry
along the common denominator to get the denominator of the
answer.
Example:
2. Addition and Subtraction when the denominators are not the same:
To add or subtract fractions that do not have the same denominator,
find a common denominator, rewrite the fractions as equivalent
fractions that have the common denominator, then add or subtract
the numerators to get the numerator of the answer and carry along
the common denominator to get the denominator of the answer.
Example:


the LCD is 4 


rewrite using the LCD 


add the numerators and carry along the LCD 
3. Adding and Subtracting if the fractions have different
denominators and you donâ€™t know the lowest common
denominator: To â€œbuildâ€ the lowest common denominator, prime
factor each denominator, and give each denominator (and
numerator) the factors that it is missing from the other
denominator.
Example:
