Adding and Subtracting Fractions

1
Adding and Subtracting Fractions

• 5.1

2
Objective

• You will be able to add and subtract fractions
• WORD WATCH
• -common denominator
• -like fractions

3

• Fractions that have the same denominators are
  called like fractions

4
Add and Subtract like fractions

• 1) add/subtract numerators
• 2) write the result over the denominator
• 3) SIMPLIFY!!!

5
EXAMPLE

5 9
2 9
7 9
5 2 9



9-1 10
9 10
1 10
8 10
4 5

-


6
? YOUR TURN!! ?

6 9
2 3
8 9
2 9
8-2 9

-


1)
1 2
5 8
7 8
57 8
12 8
2)


1


7
Add and Subtract unlike fractions

• 1) Find the LCD
• 2) Rewrite your fractions using the LCD. (you
  will now have like fractions)
• 3) Add/subtract the like fractions
• 4) SIMPLIFY

8
1 2
1 6
EVALUATE

2 1 x 2 6 2 x 3 LCD 2 x 3 6
1)

? Find the LCD
? 6
1 2
3 6
2)


? Rewrite using the LCD
1 6
1 6

3)
3 6
1 6
31 6
4 6



? Add/Subtract
2 3
4)
? SIMPLIFY
9
? YOUR TURN!! ?

5 6
7 8
17 24


1
LCD 24
5 6
20 24
21 24
7 8


20 24
2021 24
21 24
17 24
41 24



1

10
WORD PROBLEM!!

• Before a rough piece of wood can be used in
  building a house, it needs to be squared off and
  sanded. During the process, the thickness of a
  rough piece of wood inch thick is always
  reduced to inch. How much thinner is the wood
  now?

5 8
7 16
5 8
7 16
To find how much thinner the wood is, subtract
from
7 16
10 16
7 16
5 8
Rewrite using the LCD of the fractions
-

-
10 - 7 16
Rewrite using the LCD of the fractions
3 16
Simplify numerator
11
THOUGHT OF THE DAY!!

• Cats have over one hundred vocal sounds. Dogs
  only have about 10