The document discusses finding a common denominator to add or subtract fractions. It provides examples of listing the numerators of two fractions and finding the first number that appears in both lists to use as the common denominator. It then shows setting up the fractions with the common denominator and performing the addition or subtraction.

2. We need a common
denominator to add
these fractions.

3. 7, 14, 21, 28, 35…
2, 4, 6, 8, 10, 12, 14, 16, 18, 20
We need a common
denominator to add
these fractions.

4. 7, 14, 21, 28, 35…
2, 4, 6, 8, 10, 12, 14, 16, 18, 20
The first number IN COMMON
that appears on both lists
becomes the common denominator

5. x 2
x 2
X 7
x 7 7
6
7 + 6 = 13
13

6. 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

7. x 7
x 7
X 5
x 5 15
7
15 + 7 = 22
22

8. 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

9. x 7
x 7
x 8
x 8 32
21
32 + 21 = 53
53

10. 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

11. X 3
x 5
x 5
x 3
9
10
9 + 10 = 19
19

12. 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…

13. x 11
x 11
X 3
x 3 15
22
15 + 22 = 37
37

14. We need a common
denominator to add
these fractions.
3, 6, 9, 12, 15, 18, 21, 24, 27
6, 12, 18, 24,…

15. x 1
x 1
X 2
x 2 4
1
4 + 1 = 5
5

16. 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

17. x 11
x 11
X 6
x 6 18
11
29
18 + 11 = 29

18. We need a common
denominator to add
these fractions.

19. 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

20. 9, 18, 27, 36, 45, 54, 63, 72, 81
5, 10, 15, 20, 25, 30, 35, 40, 45
The first number IN COMMON
that appears on both lists
becomes the common denominator

21. x 5
x 5
x9
x 9
36
35
36 + 35 = 71
71
36 + 35 = 71

22. 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

23. x 3
x 3
x 2
x 2
19
10 + 9 = 19
9
10

24. 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…

25. x 5
x 5
x 11
x 11
4
15 - 11 = 4
15
11

26. We need a common
denominator to
subtract one fraction
from another.
2, 4, 6, 8, 10, 12, 14, 16, 18, 20 …
10, 20, 30…

27. x 1
x 1
x 5
x 5
2
5 – 3 = 2
5
3

28. Try These
A
F
E
B
C
D

29. 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.

30. Try These
A
F
E
B
C
D
17
27
19
20
10
9
41
28
26
21
13
12