Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. 4.5 Adding and Subtracting Unlike Fractions

Martin-Gay, Prealgebra, 6ed 22 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. 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, 6ed 33 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. Add: Step 1: Find the LCD of 9 and 12. LCD = 2 ∙ 2 ∙ 3 ∙ 3 = 36 Step 2: Rewrite equivalent fractions with the LCD. Adding or Subtracting Unlike Fractions 9 = 3 ∙ 3and 12 = 2 ∙ 2 ∙ 3 Continued.

Martin-Gay, Prealgebra, 6ed 44 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. Continued: Step 3: Add like fractions. Step 4: Write the sum in simplest form. Adding or Subtracting Unlike Fractions

Martin-Gay, Prealgebra, 6ed 55 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. One important application of the least common denominator is to use the LCD to help order or compare fractions. Writing Fractions in Order Insert to form a true sentence. The LCD for these fractions is 35. Write each fraction as an equivalent fraction with a denominator of 35. Continued.

Martin-Gay, Prealgebra, 6ed 66 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. Compare the numerators of the equivalent fractions. Writing Fractions in Order Continued: Since 21 > 20, then Thus,

Martin-Gay, Prealgebra, 6ed 77 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. Evaluating Expressions Evaluate x – y if x = and y =. 7 Martin-Gay, Prealgebra, 5ed Replacing x with and y with, then, x – y

Martin-Gay, Prealgebra, 6ed 88 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. Solving Equations Containing Fractions Solve: To get x by itself, add to both sides. Continued.

Martin-Gay, Prealgebra, 6ed 99 Copyright © 2011 Pearson Education, Inc. Publishing as Prentice Hall. Solving Equations Containing Fractions Write fraction in simplest form. Continued: