3-7 Adding and Subtracting Fractions
Warm Up
Lesson Presentation
Lesson Quizzes
3-7 Adding and Subtracting Fractions
Learn to add and subtract fractions.
3-7 Adding and Subtracting Fractions
Additional Example 1A: Adding or Subtracting
Fractions with Like Denominators
Add. Write the answer in simplest form.
5+1
8 8
5+ 1 = 5 + 1
8
8 8
=6= 3
4
8
Add the numerators and keep
the denominator.
Simplify.
3-7 Adding and Subtracting Fractions
Additional Example 1B: Adding or Subtracting
Fractions with Like Denominators
Subtract. Write the answer in simplest form.
9
4
–
11 11
4 = 9–4
9
–
11
11
11
= 5
11
Subtract the numerators and
keep the denominator.
The answer is in the simplest
form.
3-7 Adding and Subtracting Fractions
Check It Out: Example 1A
Add. Write the answer in simplest form.
5+1
6 6
5+ 1 = 5 + 1
6
6 6
=6= 1
6
Add the numerators and keep
the denominator.
Simplify.
3-7 Adding and Subtracting Fractions
Check It Out: Example 1B
Subtract. Write the answer in simplest form.
7
4
–
10 10
4 = 7–4
7
–
10
10
10
= 3
10
Subtract the numerators and
keep the denominator.
The answer is in the simplest
form.
3-7 Adding and Subtracting Fractions
Additional Example 1: Measurement Application
3
5
Kevin is 48 inches tall. His brother Keith is 5
8
8
inches taller. How tall is Keith ?
483 + 5 5 = 53+ 8
8
8
8
= 53 + 1
54 inches tall.
Add the integers and
add the fractions.
Rewrite8 as 1.
8
Helpful Hint
A mixed number is the sum of an integer
and a fraction: 3 4 = 3 + 4 .
5
5
3-7 Adding and Subtracting Fractions
Check It Out: Example 1
2
Alvin weighs 72 3 lbs. His baby brother weighs
15 1 lbs. How much do they weigh together?
3
72 2 + 15 1 = 87 + 3
3
3
3
= 87 + 1
Add the integers and
add the fractions.
Rewrite3 as 1.
3
Together they weigh 88 pounds.
3-7 Adding and Subtracting Fractions
Lesson Quizzes
Standard Lesson Quiz
Lesson Quiz for Student Response Systems
3-8 Adding and Subtracting Mixed Numbers
Additional Example 2A: Adding Mixed Numbers
Add. Write the answer in simplest form.
9
2 + 12 2
3
3
9 2 + 12 2 = 21 +
3
3
4
3
Add the fractions and
then add the integers.
Rewrite the improper
1
= 21 + 1
3 fraction as a mixed
1
number. Add
= 22
3
Helpful Hint
Add the fractions first in case an improper
fraction needs to be rewritten.
3-7 Adding and Subtracting Fractions
Lesson Quiz
Add or subtract. Write each answer in
simplest form.
3 5
2
1
1. 5 – 3
2. +
8 8
7 7
7
3. 5 + 1
12 2
11
12
4. 1 – 1
3 12
1
4
5. You need a nail to go through a 7 -inch door
8
1
and extend an extra inch. How long should
4
the nail be?
11 in.
8
3-7 Adding and Subtracting Fractions
Lesson Quiz for Student Response Systems
1. Add. Write your answer in simplest form.
4+5
9
9
A. 0
C. 1
9
B. 1
2
D. 1
3-7 Adding and Subtracting Fractions
Lesson Quiz for Student Response Systems
2. Subtract. Write your answer in simplest
form.
9– 5
11 11
3
11
A.
4
11
C.
B.
14
3
or 1
11
11
4
D. 1
11
3-7 Adding and Subtracting Fractions
Lesson Quiz for Student Response Systems
3. Add. Write your answer in simplest form.
3+1
8
3
A.
4
11
C.
17
24
B.
3
11
D.
24
or 1 7
17
17
3-7 Adding and Subtracting Fractions
Lesson Quiz for Student Response Systems
4. Subtract. Write your answer in simplest
form.
5 – 1
12 5
A.
4
7
C.
13
60
B.
6
7
D.
60
8
or 4
13
13
3-7 Adding and Subtracting Fractions
Lesson Quiz for Student Response Systems
8
pounds of fruits to make a
9
5
pudding. Sam has
pounds of fruits. How
12
much more does he need to make the
pudding?
5. You need
17
A.
lb
24
B.
19
lb
24
17
C.
lb
36
D.
19
lb
36