Adding & Subtracting Fractions Teacher Notes:

• Use this presentation to teach the steps for adding and subtracting fractions with unlike denominators.

• It is assumed that students have a thorough understanding of the process for making equivalent fractions.

• CLICK HERE to view a demonstration with opportunities for students to practice making equivalent fractions.

We need a common denominator to add

these fractions.

7, 14, 21, 28, 35…

2, 4, 6, 8, 10, 12, 14, 16, 18, 20

We need a common denominator to add

these fractions.

7, 14, 21, 28, 35…

2, 4, 6, 8, 10, 12, 14, 16, 18, 20

The first number IN COMMONthat appears on both lists

becomes the common denominator

x 2

x 2

X 7

x 7 7

6

7 + 6 = 13

13

We need a common denominator to add

these fractions.

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

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

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.

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

6, 12, 18, 24,…

x 1

x 1

X 2

x 2 4

1

4 + 1 = 5 5

We need a common denominator to add

these fractions.

11, 22, 33, 44, 55, 66, 77…

6, 12, 18, 24, 30, 36, 42, 48, 54, 60, 66, 72

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.

9, 18, 27, 36, 45, 54, 63, 72, 81

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

9, 18, 27, 36, 45, 54, 63, 72, 81

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

The first number IN COMMONthat appears on both lists

becomes the common denominator

x 5

x 5

x9

x 936

3536 + 35 = 71

71

36 + 35 = 71

We need a common denominator to add

these fractions.

12, 24, 36, 48, 60, 72, 84, 96

8, 16, 24, 32, 40, 48, 56, 64, 72, 79, 80, 88, 96

x 3

x 3

x 2

x 2

19

10 + 9 = 19

9

10

5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55

We need a common denominator to

subtract a fraction from another.

11, 22, 33, 44, 55, 66, 77…

x 5

x 5

x 11

x 11

4

15 - 11 = 4

15

11

We need a common denominator to

subtract one fractionfrom another.

2, 4, 6, 8, 10, 12, 14, 16, 18, 20 …

10, 20, 30…

x 1

x 1

x 5

x 5

2

5 – 3 = 2

5

3

Try These

A

F

EB

C

D

Answers On Next Slide

• Each click on the next slide reveals an answer.

• Check your papers.

• If you discover an incorrect answer, be able to explain your mistake.

Try These

A

F

EB

C

D1727

1920

109

4128

2621

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