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

2. 5-7 Adding and Subtracting with Unlike Denominators Warm Up 1. + 2. +
Course 1
5-7
Adding and Subtracting with Unlike Denominators
Warm Up
Add. Write each answer in simplest form. 1 7 __ 1 7 __ 8 15 __ 3 15 __ 2 7 __ 11 15 __ 7 9 __ 2 9 __ 11 20 __ 4 20 __ 3 4 __ 1

3. 5-7 Adding and Subtracting with Unlike Denominators Problem of the Day
Course 1
5-7
Adding and Subtracting with Unlike Denominators
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

4. 5-7 Learn to add and subtract fractions with unlike denominators.
Course 1
5-7
Adding and Subtracting with Unlike Denominators
Learn to add and subtract fractions with unlike denominators.

5. Insert Lesson Title Here
Course 1
5-7
Adding and Subtracting with Unlike Denominators
Insert Lesson Title Here
Vocabulary
least common denominator (LCD)

6. 5-7 Adding and Subtracting with Unlike Denominators
Course 1
5-7
Adding and Subtracting with Unlike Denominators 1 3 __
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 5 __ 1 3 __ 1 5 __

7. 5-7 Adding and Subtracting with Unlike Denominators
Course 1
5-7
Adding and Subtracting with Unlike Denominators
To add or subtract unlike fractions, first rewrite them as equivalent fractions with a common denominator.
Remember!
Fractions that represent the same value are equivalent.

8. Additional Example 1: Cooking Application
Course 1
5-7
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 or onions? 1 4 __ 1 3 __ 1 4 __ 3
Add + ? 1 4 __ 3 1 4 __ 1 3 __ +
_____
Find a common denominator for 4 and 3. 1 4 __

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

10. 5-7 Adding and Subtracting with Unlike Denominators
Course 1
5-7
Adding and Subtracting with Unlike Denominators
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 __ 1 2 __ 1 3 __ 2
Add + 1 3 __ 1 2 __ 1 3 __ ? 1 2 __ +
_____
Find a common denominator for 3 and 2.

11. Try This: Example 1 Continued
Course 1
5-7
Adding and Subtracting with Unlike Denominators
Try This: Example 1 Continued 1 3 __ 2 6 __
Write equivalent fractions with 6 as the common denominator. 1 2 __ 3 6 __
Add the numerators. Keep the common denominator. +
_______
_____ 5 6 __ 1 3 __ 2 6 5 6 __
The peppers or ham cover of the pizza.

12. Course 1
5-7
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.

13. Additional Example 2A: Adding and Subtracting Unlike Fractions
Course 1
5-7
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.
A – 7 10 __ 3 8 __ 7 10 __ 3 8 __ –
Multiply the denominators. 10 • 8 = 80 56 80 __ 30 80 __ –
Write equivalent fractions. 26 80 __
Subtract. 13 40 __
Write the answer in simplest form.

14. Additional Example 2B: Adding and Subtracting Unlike Fractions
Course 1
5-7
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.
B – 11 12 __ 3 8 __ 11 12 __ 3 8 __ –
The LCD is 24. 22 24 __ 9 24 __ –
Write equivalent fractions. 13 24 __
Subtract.

15. Additional Example 2C: Adding and Subtracting Unlike Fractions
Course 1
5-7
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. C 5 16 __ 1 8 __ 5 16 __ 1 8 __
Think: 16 is a multiple of 8, so the LCD is 16. + 5 16 __ 2 16 __ 1 8 __ +
Rewrite with a denominator of 16. 7 16 __
Add.

16. Additional Example 2D: Adding and Subtracting Unlike Fractions
Course 1
5-7
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.
D – 5 16 __ 1 8 __ 5 16 __ 1 8 __
Think: 16 is a multiple of 8, so the LCD is 16. – 5 16 __ 2 16 __ 1 8 __ –
Rewrite with a denominator of 16. 3 16 __
Subtract.

17. 5-7 Adding and Subtracting with Unlike Denominators
Course 1
5-7
Adding and Subtracting with Unlike Denominators
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. 10 • 6 = 60 48 60 __ 20 60 __ –
Write equivalent fractions. 28 60 __
Subtract. 7 15 __
Write the answer in simplest form.

18. 5-7 Adding and Subtracting with Unlike Denominators
Course 1
5-7
Adding and Subtracting with Unlike Denominators
Try This: Example 2B
Add or Subtract. Write each answer in simplest form.
Method 2: Use the LCD.
B – 4 7 __ 1 3 __ 4 7 __ 1 3 __ –
The LCD is 21. 12 21 __ 7 21 __ –
Write equivalent fractions. 5 21 __
Subtract.

19. 5-7 Adding and Subtracting with Unlike Denominators
Course 1
5-7
Adding and Subtracting with Unlike Denominators
Try This: Example 2C
Add or Subtract. Write each answer in simplest form.
Method 3: Use mental math. C 3 12 __ 1 6 __ 3 12 __ 1 6 __
Think: 12 is a multiple of 6, so the LCD is 12. + 3 12 __ 2 12 __ 1 6 __ +
Rewrite with a denominator of 12. 5 12 __
Add.

20. 5-7 Adding and Subtracting with Unlike Denominators
Course 1
5-7
Adding and Subtracting with Unlike Denominators
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 __
Think: 12 is a multiple of 6, so the LCD is 12. – 3 12 __ 2 12 __ 1 6 __ –
Rewrite with a denominator of 12. 1 12 __
Subtract.

21. Insert Lesson Title Here
Course 1
5-7
Adding and Subtracting with Unlike Denominators
Insert Lesson Title Here
Lesson Quiz
Add or Subtract. Write each answer in simplest form. – –
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 __ 13 24 __ 1 2 __ 1 8 __ 3 8 __ 5 12 __ 1 6 __ 1 4 __ 1 6 __ 1 8 __ 7 24 __ 3 4 __ 1 3 __ 5 12 __
cup