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Warm Up

Problem of the Day

Lesson Presentation

Lesson Quizzes

Warm Up Add or subtract.

2 5

3 5

1.

1

7 12

11 12

2.

3 2

3. 6.5 (1.2)

5.3

4. 3.4 0.9

2.5

Problem of the Day The least common multiple of

6 and a number is 24. What is the other number?

8 or 24

Learn to add and subtract fractions with unlike

denominators.

Two hikers on the Appalachian Trail are 5 from

the trail ahead. The hikers walk 2 miles before

taking a break. They then hike another 1 miles

before taking a second break. How many more miles

do they have to hike before reaching the summit?

To solve this problem, add and subtract rational

numbers with unlike denominators. First find a

common denominator using one of the following

methods

Method 1 Find a common denominator by

multiplying one denominator by the other

denominator.

Method 2 Find the least common denominator (LCD).

Additional Example 1A Adding and Subtracting

Fractions with Unlike Denominators

Add or Subtract. Method 1

Find a common denominator 8(7)56.

2 7

1 8

A.

Multiply by fractions equal to 1.

Rewrite with a common denominator. Simplify.

Additional Example 1B Adding and Subtracting

Fractions with Unlike Denominators

Add or Subtract. Method 2

Write as improper fractions.

1 6

5 8

1

1

B.

List the multiples of each denominator and find

the LCD

Multiply by fractions equal to 1.

Rewrite with a common denominator.

Simplify.

(No Transcript)

Check It Out Example 1A

Add or Subtract. Method 1

Find a common denominator 3(8)24.

5 8

1 3

A.

Multiply by fractions equal to 1.

Rewrite with a common denominator.

Check It Out Example 1B

Add or Subtract. Method 2

Write as an improper fraction.

1 6

3 4

2

B.

List the multiples of each denominator and find

the LCD

Multiply by fractions equal to 1.

Rewrite with a common denominator.

Simplify.

Additional Example 2 Evaluating Expressions with

Rational Numbers

4 5

5 6

Evaluate t for t .

Multiply by fractions equal to 1.

Rewrite with a common denominator 6(5) 30.

Check It Out Example 2

Multiply by fractions equal to 1.

Rewrite with lowest common denominator (36).

Simplify.

Additional Example 3 Consumer Application

Two dancers are making necklaces from ribbon for

their costumes. They need pieces measuring 13

inches and 12 inches. How much ribbon will be

left over after the pieces are cut from a 36-inch

length?

Subtract both amounts from 36 to find the amount

of ribbon left.

Write as improper fractions. The LCD is 8.

Rewrite with a common denominator.

Simplify.

Check It Out Example 3

Fred and Jose are building a tree house. They

need to cut a 6 foot piece of wood and a 4

foot piece of wood from a 12 foot board. How

much of the board will be left?

Subtract both amounts from 12 to find the amount

of board left.

Write as improper fractions. The LCD is 12.

Rewrite with a common denominator.

Simplify.

Lesson Quizzes

Standard Lesson Quiz

Lesson Quiz for Student Response Systems

Lesson Quiz

Add or subtract.

5 14

1 7

1.

12

2 3

2.

8

1

3 5

2 3

3.

2

38

9 16

4. Evaluate n for n .

1

12

Robert is 5 feet 6 inches tall. Judy is 5 feet

3 inches tall. How much taller is Robert than

Judy?

5.

3 4

Lesson Quiz for Student Response Systems

1. Add. A. C. 1 B. D. 1

7 12

1 6

1 2

1 3

3 4

1 2

Lesson Quiz for Student Response Systems

2. Subtract. 8 6 A. 2 C. 3 B.

2 D. 3

3 4

1 4

1 2

3 4

1 4

Lesson Quiz for Student Response Systems

3. Add or subtract. 3 A. 2 C.

2 B. 2 D. 2

8 9

1 2

11 18

1 3

1 3

4 9

Lesson Quiz for Student Response Systems

1 7

5 14

4. Evaluate 1 x for x . A. 1 C.

B. D.

11 14

13 14

9 14

Lesson Quiz for Student Response Systems

1 4

5. A pine tree is 20 feet 3 inches tall.

Another pine tree is 20 feet 5 inches tall.

How much taller is the second pine tree than

the first? A. 2 in. C. 3 in. B. 2

in. D. 3 in.

3 4

1 4

1 4

1 2

1 2