Fractions

• Like denominators- just add the numerator.

• Example: 2/5 + 2/5= 4/5

Like Denominators

• Guided Practice:

12/ 15 + 2/15

Try on your own: 6/23 + 7/23

Unlike denominators

• Step 1: find the LCM of the denominators Step 2: multiply both the top and the bottom by that number

• Step 3: Make sure it doesn’t need to be simplified

• Look at the next slide for example

We need a common denominator to add

these fractions.

x 2

x 2

X 7

x 7 7

6

7 + 6 = 13

13

We need a common denominator to add

these fractions.

x 7

x 7

X 5

x 5 15

7

15 + 7 = 22

22

We need a common denominator to add

these fractions.

7, 14, 21, 28, 35, 42, 49, 56, 63

8, 16, 24, 32, 40, 48, 56, 64, 72

x 7

x 7

x 8

x 8 32

2132 + 21 = 53

53

We need a common denominator to add

these fractions.

3, 6, 9, 12, 15, 18, 21, 24, 27

5, 10, 15, 20, 25, 30, 35, 40, 45

X 3

x 5

x 5

x 3 9

10

9 + 10 = 19

19

We need a common denominator to add

these fractions.

3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33

11, 22, 33, 44, 55, 66, 77…

x 11

x 11

X 3

x 3 15

2215 + 22 = 37

37

We need a common denominator to add

these fractions.

x 11

x 11

X 6

x 6 18

11

29

18 + 11 = 29

We need a common denominator to add

these fractions.

We need a common denominator to add

these fractions.

x 5

x 5

x9

x 936

3536 + 35 = 71

71

36 + 35 = 71

Try These

A

F

EB

C

D

Try These

A

F

EB

C

D1727

1920

109

4128

2621

1312

Subtracting Fractions

• The steps are just like adding fractions, but instead of adding the numerators, you subtract the numerators.

We need a common denominator to

subtract a fraction from another.

x 5

x 5

x 11

x 11

4

15 - 11 = 4

15

11

x 1

x 1

x 5

x 5

2

5 – 3 = 2

5

3