1. Adding and Subtracting Unlike Fractions
Chapter 1 / Whole Numbers and Introduction to Algebra
Section 4.5
Adding and Subtracting Unlike Fractions

2. Adding or Subtracting Unlike Fractions
Chapter 1 / Whole Numbers and Introduction to Algebra
Adding or Subtracting Unlike Fractions
Step 1. Find the LCD of the denominators of the fractions.
Step 2. Write each fraction as an equivalent fraction whose denominator is the LCD.
Step 3. Add or subtract the like fractions.
Step 4. Write the sum or difference in simplest form.
Martin-Gay, Prealgebra, 5ed

3. Chapter 1 / Whole Numbers and Introduction to Algebra
Add:
Step 1: Find the LCD of 9 and 12.
and
LCD =
Step 2: Rewrite equivalent fractions with the LCD.
Martin-Gay, Prealgebra, 5ed

4. Chapter 1 / Whole Numbers and Introduction to Algebra
Add:
Step 3: Add like fractions.
Step 4: Write the sum in simplest form.
is in simplest form.
Martin-Gay, Prealgebra, 5ed

5. Chapter 1 / Whole Numbers and Introduction to Algebra
Writing Fractions in Order
One important application of the least common denominator is to use the LCD to help order or compare fractions.
Insert < or > to form a true sentence.
The LCD for these fractions is 35.
Write each fraction as an equivalent fraction with a denominator of 35.
Martin-Gay, Prealgebra, 5ed

6. Chapter 1 / Whole Numbers and Introduction to Algebra
Writing Fractions in Order . . .
Compare the numerators of the equivalent fractions.
Since 21 > 20, then
Thus,
Martin-Gay, Prealgebra, 5ed

7. Chapter 1 / Whole Numbers and Introduction to Algebra
Evaluating Expressions Given Fractional Replacement Values
Evaluate x - y if x = and y = .
Replacing x with and y with ,
then, x - y =
x - y =
Martin-Gay, Prealgebra, 5ed

8. Chapter 1 / Whole Numbers and Introduction to Algebra
Solving Equations Containing Fractions
Solve:
To get x by itself, add to both sides.
Write fraction in simplest form
Martin-Gay, Prealgebra, 5ed