1. Course 1 5-2 Adding and Subtracting with Unlike Denominators 5-2 Adding and Subtracting with Unlike Denominators Course 1 Warm Up Warm Up Lesson Presentation Lesson Presentation Problem of the Day Problem of the Day

2. Course 1 5-2 Adding and Subtracting with Unlike Denominators Learn to add and subtract fractions with unlike denominators.

3. Course 1 5-2 Adding and Subtracting with Unlike Denominators Vocabulary least common denominator (LCD)

4. Course 1 5-2 Adding and Subtracting with Unlike Denominators 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 __ 1 3 1 5 1 5

5. Course 1 5-2 Adding and Subtracting with Unlike Denominators Fractions that represent the same value are equivalent. Remember! To add or subtract unlike fractions, first rewrite them as equivalent fractions with a common denominator.

6. Course 1 5-2 Adding and Subtracting with Unlike Denominators 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 and onions? 1 4 __ 1 3 1 4 1 3 _____ + Find a common denominator for 4 and 3. ? 1 4 __ 1 3 1 4 1 3 Add +.

7. Course 1 5-2 Adding and Subtracting with Unlike Denominators Additional Example 1 Continued Write equivalent fractions with 12 as the common denominator. 1 4 __ 1 3 _______ + 3 12 __ 4 12 __ _____ Add the numerators. Keep the common denominator. 1 4 __ 1 3 7 12 __ 1 12 1 12 1 12 1 12 1 12 1 12 1 12 The pepperoni and onions cover of the pizza. 7 12 __

8. Course 1 5-2 Adding and Subtracting with Unlike Denominators Check It Out: 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 and peppers? 1 3 __ 1 2 1 3 1 2 ? 1 3 1 2 _____ + Find a common denominator for 3 and 2. 1 3 __ 1 2 Add +.

9. Course 1 5-2 Adding and Subtracting with Unlike Denominators Check It Out: Example 1 Continued Write equivalent fractions with 6 as the common denominator. 1 3 __ 1 2 _______ + 2 6 __ 3 6 _____ Add the numerators. Keep the common denominator. 5 6 __ 1 3 1 2 1616 1616 1616 1616 1616 The peppers and ham cover of the pizza. 5 6 __

10. Course 1 5-2 Adding and Subtracting with Unlike Denominators 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.

11. Course 1 5-2 Adding and Subtracting with Unlike Denominators Additional Example 2A: Adding and Subtracting Unlike Fractions Add or Subtract. Write each answer in simplest form. Method 1: Multiplying denominators. 7 10 __ 3 8 – 7 10 __ 3 8 – 56 80 __ 30 80 __ Multiply the denominators. 10 8 = 80 Write equivalent fractions with a common denominator. Subtract. Write the answer in simplest form. 26 80 __ 13 40 __ –

12. Course 1 5-2 Adding and Subtracting with Unlike Denominators Additional Example 2B: Adding and Subtracting Unlike Fractions Add or Subtract. Write each answer in simplest form. Method 2: Use the LCD. – 11 12 __ 3 8 – 11 12 __ 3 8 – 22 24 __ 9 24 __ Multiples of 8: 8, 16, 24, … The LCD is 24. Write equivalent fractions with a common denominator. Subtract. 13 24 __ Multiples of 12: 12, 24, …

13. Course 1 5-2 Adding and Subtracting with Unlike Denominators Additional Example 2C: Adding and Subtracting Unlike Fractions Add or Subtract. Write each answer in simplest form. Method 3: Use mental math. 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. Add. 7 16 __ 1 8 +

14. Course 1 5-2 Adding and Subtracting with Unlike Denominators Additional Example 2D: Adding and Subtracting Unlike Fractions Add or Subtract. Write each answer in simplest form. Method 3: Use mental math. 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. 3 16 __ 1 8 –

15. Course 1 5-2 Adding and Subtracting with Unlike Denominators Check It Out: Example 2A Add or Subtract. Write each answer in simplest form. Method 1: Multiplying denominators. – 8 10 __ 2 6 – 8 10 __ 2 6 – 48 60 __ 20 60 __ Multiply the denominators. 10 6 = 60 Write equivalent fractions with a common denominator. Subtract. Write the answer in simplest form. 28 60 __ 7 15 __

16. Course 1 5-2 Adding and Subtracting with Unlike Denominators Check It Out: Example 2B Add or Subtract. Write each answer in simplest form. Method 2: Use the LCD. – 4 7 __ 1 3 – 4 7 1 3 – 12 21 __ 7 21 __ Multiples of 3: 3, 6, 9, 12, 15, 18, 21, … The LCD is 21. Write equivalent fractions. Subtract. 5 21 __ Multiples of 7: 7, 14, 21, …

17. Course 1 5-2 Adding and Subtracting with Unlike Denominators Check It Out: Example 2C Add or Subtract. Write each answer in simplest form. Method 3: Use mental math. 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. Add. 5 12 __ 1 6 +

18. Course 1 5-2 Adding and Subtracting with Unlike Denominators Check It Out: Example 2D Add or Subtract. Write each answer in simplest form. Method 3: Use mental math. 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 12 __ 1 6 –

19. Course 1 5-2 Adding and Subtracting with Unlike Denominators Lesson Quiz Add or subtract. Write each answer in simplest form. 1. +2. – 3. – 4. + 5. 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? 3 8 __ 1 6 1 2 1 8 5 12 __ 1 6 1 6 1 8 3 4 1 3 13 24 __ 3 8 1 4 7 24 __ 5 12 __ cup