Chapter 7 Add and Subtract Fractions

What You Will Learn To find a common denominator and use it to write equivalent fractions To add and subtract fractions with unlike denominators To add and subtract mixed numbers To solve fraction problems

Key Words Multiple Common Denominator Improper Fraction Mixed Number

7.1 – Common Denominators After this lesson, you will be able to:  Find a common denominator to a set of fractions  Compare and order positive fractions Key Terms  Common Denominator A common multiple of the denominators of a set of fractions Ex: A common denominator for ¼ and 1/6 is 12 because a common multiple of 4 and 6 is 12.  Multiple The product of a given number and a natural number like, 1, 2, 3, and so on Ex: Some multiples of 3 are 3, 6, 9, 12, and 15, etc…

Determine a Common Denominator Method 1: Paper Folding or Diagrams  A) Determine a common denominator for 2/3 and ½.  B) Determine Equivalent fractions for 2/3 and ½ using the common denominator from A). A common denominator for 2/3 and ½ is 6. Shade 2/3 of the rectangle red. 4 of the 6 parts are red. 2/3 = 4/6 Shade ½ of the rectangle blue. 3 of the 6 parts are red. ½ = 3/6

Determine a Common Denominator Method 2: Use Multiples

Key Ideas You can use paper folding, diagrams, or multiples to determine a common denominator.  Paper Folding or Diagram To write fractions with a common denominator, determine equivalent fractions. ___ = ___ __ of the ___ parts are blue. ___ = ___ __ of the __ parts are red. ___ = ___

7.2 – Add and Subtract Fractions With Unlike Denominators After this lesson, you will be able to:  Add and subtract fractions with unlike denominators  Solve problems involving the addition and subtraction of fractions  Check that your answers are reasonable using estimation

Key Ideas When adding and subtracting fractions using models or diagrams, show each fraction using parts of the whole that are of equal size. Pattern BlocksDiagram Pattern Blocks ½ + 1/3 = 3/6 + 2/62/3 – 1/6 = 4/6 – 1/6 To add or subtract fractions with unlike denominators, use a common denominator. You can estimate when adding or subtracting fractions by comparing fractions to 0, ½, or 1.

Assignment Show You Know, p. 239 Show You Know, p. 241 P. 241  # 1-4, 6, 9, 11, 16, 17  Still Good? #18, 22  Pro Star? #15, , 23