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 1: Simplify the fol lowing .
2. Addition and Subtraction When the Denominators Are
Not the
Same: To add or subtract fractions that do not have the same
denominator:
• Find the least common denominator (LCD).
• Rewrite the fractions as equivalent fractions that have the LCD
as their 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.
NOTE: On tests, when adding or subtracting fractions, you
must
rewrite the fractions as equivalent fractions that have the least
common denominator. This step is worth points, and to get the points
your denominator must be the least common denominator.
Example 2: Simplify the following.
 |
the LCD is 4 |
 |
rewrite using the LCD and adjusting the
numerators |
 |
add the numerators and carry along the LCD |
3. Addition and Subtraction If the Fractions Have
Different
Denominators and You Don’t Know the Least Common
Denominator (LCD): To “build” the least common denominator,
prime factor each denominator , and give each denominator (and
numerator) the factors that it is missing from the other denominator.
Example 3: Simplify the following.
Practice Problems:
Simplify each of the following.
Answers to Practice Problems:
