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3-8

3-8. Adding and Subtracting Fractions. Course 2. Warm Up. Problem of the Day. Lesson Presentation. 3-8. Adding and Subtracting Fractions. Course 2. Additional Example 1A: Adding or Subtracting Fractions with Like Denominators. Add. Write the answer in simplest form. 5 8. 1 8. +.

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3-8

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  1. 3-8 Adding and Subtracting Fractions Course 2 Warm Up Problem of the Day Lesson Presentation

  2. 3-8 Adding and Subtracting Fractions Course 2 Additional Example 1A: Adding or Subtracting Fractions with Like Denominators Add. Write the answer in simplest form. 5 8 1 8 + 5 + 1 5 8 1 8 Add the numerators and keep the denominator. + = 8 3 4 6 8 = = Simplify.

  3. 3-8 Adding and Subtracting Fractions 5 11 = Course 2 Additional Example 1B: Adding or Subtracting Fractions with Like Denominators Subtract. Write the answer in simplest form. 9 11 4 11 – Subtract the numerators and keep the denominator. 4 11 9 11 9 – 4 = – 11 The answer is in the simplest form.

  4. 3-8 Adding and Subtracting Fractions Helpful Hint The LCM of two denominators is the lowest common denominator (LCD) of the fractions. Course 2 To add or subtract fractions with different denominators, you must rewrite the fractions with a common denominator.

  5. 3-8 Adding and Subtracting Fractions 8 12 9 12 – = 1 12 = – Course 2 Additional Example 2B: Adding and Subtracting Fractions with Unlike Denominators Subtract. Write the answer in simplest form. 2 3 3 4 – 3 · 3 2 · 4 2 3 3 4 – – = Multiply the denominators. 3 · 4 4 · 3 Write equivalent fractions using the common denominator. Subtract.

  6. 3-8 Adding and Subtracting Fractions Course 2 Additional Example 2A: Adding and Subtracting Fractions with Unlike Denominators Add. Write the answer in simplest form. 5 6 7 8 + 5 · 4 6 · 4 7 · 3 8 · 3 5 6 7 8 = + The LCM of the denominator is 24. + 21 24 20 24 Write equivalent fractions using the common denominator. = + 41 24 17 24 = = Divide. 1

  7. 3-8 Adding and Subtracting Fractions 2 7 1 3 1 · 7 3 · 7 2 · 3 7 · 3 + – = – + 6 21 7 21 = + – 1 21 Course 2 Additional Example 2C: Adding and Subtracting Fractions with Unlike Denominators Add. Write the answer in simplest form. 2 7 1 3 – + Multiply the denominators. Write equivalent fractions using the common denominator. = Add.

  8. 3-8 Adding and Subtracting Fractions Course 2 Check It Out: Example 2A Add. Write the answer in simplest form. 2 5 5 6 + 2 · 6 5 · 6 5 · 5 6 · 5 2 5 5 6 = + Multiply the denominators. + 25 30 12 30 Write equivalent fractions using the common denominator. = + 37 30 7 30 = = Divide. 1

  9. 3-8 Adding and Subtracting Fractions 4 10 5 10 – = 1 10 = Course 2 Check It Out: Example 2B Subtract. Write the answer in simplest form. 1 2 2 5 – 1 · 5 2 · 2 2 5 1 2 – – = Multiply the denominators. 5 · 2 2 · 5 Write equivalent fractions using the common denominator. Subtract. –

  10. 3-8 Adding and Subtracting Fractions 3 5 1 2 1 · 5 2 · 5 3 · 2 5 · 2 + – = – + 6 10 5 10 = + – 1 10 Course 2 Check It Out: Example 2C Add. Write the answer in simplest form. 3 5 1 2 – + Multiply the denominators. Write equivalent fractions using the common denominator. = – Add.

  11. 3-8 Adding and Subtracting Fractions 5 12 5 12 1 2 1 · 6 5 · 1 12 · 1 – – = 2 · 6 5 12 6 12 = – 1 12 = 1 12 It takes Luke hour longer to drive to work. Course 2 Check It Out: Example 3 It takes Michelle hour to drive to work. It takes Luke hour to drive to work. How much longer does it take Luke to drive to work? 1 2 The LCM of the denominators is 12. Write equivalent fractions using the common denominator. Subtract.

  12. They have different signs, so what operation will you do after you find a common denominator?

  13. Subtractions = KFC

  14. Subtractions = KFC

  15. Let’s Practice • Turn to page 31 • Check with your partner to see if you two are getting the same answers.

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