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5-7 Adding and Subtracting with Unlike Denominators Course 1 Warm Up Warm Up Lesson Presentation Lesson Presentation Problem of the Day Problem of the Day

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Course Adding and Subtracting with Unlike Denominators Warm Up Add. Write each answer in simplest form __ __ 3 15 __ __ 4 20 __ __ 1 3 4

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Problem of the Day If it takes 12 minutes to cut a pipe into three pieces, how long would it take to cut the pipe into four pieces. 18 minutes Course Adding and Subtracting with Unlike Denominators

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Learn to add and subtract fractions with unlike denominators. Course Adding and Subtracting with Unlike Denominators

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Vocabulary least common denominator (LCD) Insert Lesson Title Here Course Adding and Subtracting with Unlike Denominators

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The Pacific Ocean covers of Earth’s surface. The Atlantic Ocean covers of Earth’s surface. To find the fraction of the Earth’s surface that is covered by both oceans, you can add and, which are unlike fractions. 1 3 __ Course Adding and Subtracting with Unlike Denominators

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Fractions that represent the same value are equivalent. Remember! Course Adding and Subtracting with Unlike Denominators To add or subtract unlike fractions, first rewrite them as equivalent fractions with a common denominator.

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Additional Example 1: Cooking Application Mark made a pizza with pepperoni covering of the pizza and onions covering another. What fraction of the pizza is covered by pepperoni or onions? 1 4 __ _____ + Find a common denominator for 4 and 3. Course Adding and Subtracting with Unlike Denominators ? 1 4 __ Add +

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Additional Example 1 Continued Write equivalent fractions with 12 as the common denominator. 1 4 __ 1 3 _______ __ 4 12 __ _____ Add the numerators. Keep the common denominator. 1 4 __ __ The pepperoni or onions cover of the pizza __ Course Adding and Subtracting with Unlike Denominators

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Try This: Example 1 Tori made a pizza with peppers covering of the pizza and ham covering another. What fraction of the pizza is covered by ham or peppers? 1 3 __ ? _____ + Find a common denominator for 3 and 2. Course Adding and Subtracting with Unlike Denominators 1 3 __ 1 2 Add +

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Try This: Example 1 Continued Write equivalent fractions with 6 as the common denominator. 1 3 __ 1 2 _______ __ 3 6 _____ Add the numerators. Keep the common denominator. 5 6 __ The peppers or ham cover of the pizza. 5 6 __ Course Adding and Subtracting with Unlike Denominators

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You can use any common denominator or the least common denominator to add and subtract unlike fractions. The least common denominator (LCD) is the least common multiple of the denominators. Course Adding and Subtracting with Unlike Denominators

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Additional Example 2A: Adding and Subtracting Unlike Fractions Add or Subtract. Write each answer in simplest form. Method 1: Multiplying denominators. A. – 7 10 __ 3 8 – 7 10 __ 3 8 – __ __ Multiply the denominators = 80 Write equivalent fractions. Subtract. Write the answer in simplest form __ __ Course Adding and Subtracting with Unlike Denominators

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Additional Example 2B: Adding and Subtracting Unlike Fractions Add or Subtract. Write each answer in simplest form. Method 2: Use the LCD. B. – __ 3 8 – __ 3 8 – __ 9 24 __ The LCD is 24. Write equivalent fractions. Subtract __ Course Adding and Subtracting with Unlike Denominators

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Additional Example 2C: Adding and Subtracting Unlike Fractions Add or Subtract. Write each answer in simplest form. Method 3: Use mental math. C __ __ __ 2 16 __ Think: 16 is a multiple of 8, so the LCD is 16. Rewrite with a denominator of 16. Add __ 1 8 Course Adding and Subtracting with Unlike Denominators

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Additional Example 2D: Adding and Subtracting Unlike Fractions Add or Subtract. Write each answer in simplest form. Method 3: Use mental math. D. – 5 16 __ 1 8 – 5 16 __ 1 8 – 5 16 __ 2 16 __ Think: 16 is a multiple of 8, so the LCD is 16. Rewrite with a denominator of 16. Subtract __ Course Adding and Subtracting with Unlike Denominators 1 8 __

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Try This: Example 2A Add or Subtract. Write each answer in simplest form. Method 1: Multiplying denominators. A. – 8 10 __ 2 6 – 8 10 __ 2 6 – __ __ Multiply the denominators = 60 Write equivalent fractions. Subtract. Write the answer in simplest form __ 7 15 __ Course Adding and Subtracting with Unlike Denominators

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Try This: Example 2B Add or Subtract. Write each answer in simplest form. Method 2: Use the LCD. B. – 4 7 __ 1 3 – – __ 7 21 __ The LCD is 21. Write equivalent fractions. Subtract __ Course Adding and Subtracting with Unlike Denominators

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Try This: Example 2C Add or Subtract. Write each answer in simplest form. Method 3: Use mental math. C __ __ __ 2 12 __ Think: 12 is a multiple of 6, so the LCD is 12. Rewrite with a denominator of 12. Add __ 1 6 Course Adding and Subtracting with Unlike Denominators

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Try This: Example 2D Add or Subtract. Write each answer in simplest form. Method 3: Use mental math. D. – 3 12 __ 1 6 – 3 12 __ 1 6 – 3 12 __ 2 12 __ Think: 12 is a multiple of 6, so the LCD is 12. Rewrite with a denominator of 12. Subtract __ 1 6 Course Adding and Subtracting with Unlike Denominators

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Lesson Quiz Add or Subtract. Write each answer in simplest form – 3. – Bonnie is making oatmeal bars and the recipes calls for cup of brown sugar. If she has cup of brown sugar, how much more does she need? Insert Lesson Title Here 3 8 __ __ __ __ 5 12 __ cup Course Adding and Subtracting with Unlike Denominators

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