This presentation teaches how to perform operations on fractions, including: - Adding fractions by making the denominators the same - Subtracting fractions by making the denominators the same - Multiplying fractions by multiplying the numerators and denominators - Dividing fractions by turning the second fraction upside down and changing the division to multiplication It also explains how to find a common denominator to allow adding or subtracting fractions with different denominators, which involves multiplying the denominators and adjusting the numerators accordingly. Examples are provided for each operation.

1. Fractions
This presentation will help you to:
• add
• subtract
• multiply and
• divide fractions

2. Adding fractions
To add fractions together the
denominator (the bottom bit) must be
the same.
Example
=+
8
2
8
1

3. Adding fractions
To add fractions together the
denominator (the bottom bit) must be
the same.
Example
=+
8
2
8
1
=
+
8
21

4. Adding fractions
To add fractions together the
denominator (the bottom bit) must be
the same.
Example
=+
8
2
8
1
=
+
8
21
8
3

5. Now try these
Click to see the next slide to reveal the answers.
1. 2.
3. 4.
=+
3
1
3
1
=+
12
7
12
3
=+
7
4
7
2
=+
4
1
4
2

6. Now try these
1. 2.
3. 4.
=+
3
1
3
1
=+
12
7
12
3
=+
7
4
7
2
=+
4
1
4
2
3
2
4
3
7
6
12
10

7. Subtracting fractions
=−
8
2
8
3
To subtract fractions the denominator (the bottom
bit) must be the same.
Example

8. Subtracting fractions
=−
8
2
8
3
=
−
8
23
To subtract fractions the denominator (the bottom
bit) must be the same.
Example

9. Subtracting fractions
=−
8
2
8
3
=
−
8
23
8
1
To subtract fractions the denominator (the bottom
bit) must be the same.
Example

10. Now try these
Click on the next slide to reveal the answers.
1. 2.
3. 4.
=−
3
1
3
2
=−
12
3
12
7
=−
7
3
7
4
=−
4
1
4
2

11. Now try these
.
1. 2.
3. 4.
=−
3
1
3
2
=−
12
3
12
7
=−
7
3
7
4
=−
4
1
4
2
3
1
4
1
7
1
12
4

12. Multiplying fractions
To multiply fractions we multiply
the tops and multiply the bottoms
Top x Top
Bottom x Bottom

13. Multiplying fractions
Example
=×
3
1
2
1

14. Multiplying fractions
Example
=×
3
1
2
1
=
×
×
32
11

15. Multiplying fractions
Example
=×
3
1
2
1
=
×
×
32
11
6
1

16. Now try these
Click on the next slide to reveal the answers.
1. 2.
3. 4.
=×
3
1
3
1
=×
5
3
3
1
=×
5
4
4
2
=×
4
1
4
2

17. Now try these
.
1. 2.
3. 4.
=×
3
1
3
1
=×
5
3
3
1
=×
5
4
4
2
=×
4
1
4
2
9
1
16
2
20
8
15
3

18. Dividing fractions
Once you know a simple trick,
dividing is as easy as multiplying!
• Turn the second fraction upside down
• Change the divide to multiply
• Then multiply!

19. Dividing fractions
•Turn the second fraction upside down
Example ?=÷
3
1
6
1
1
3
6
1
÷

20. Dividing fractions
•Turn the second fraction upside down
Example ?=÷
3
1
6
1
1
3
6
1
÷
•Change the divide into a multiply
1
3
6
1
×

21. Dividing fractions
•Turn the second fraction upside down
Example ?=÷
3
1
6
1
1
3
6
1
÷
•Change the divide into a multiply
1
3
6
1
×
•Then multiply =
×
×
=×
16
31
1
3
6
1

22. Dividing fractions
•Turn the second fraction upside down
Example ?=÷
3
1
6
1
1
3
6
1
÷
•Change the divide into a multiply
1
3
6
1
×
•Then multiply =
×
×
=×
16
31
1
3
6
1
6
3

23. Now try these
Click on the next screen to reveal the answers.
1. 2.
3. 4.
=÷
2
1
3
1
=÷
5
4
2
1
=÷
6
2
4
1
=÷
3
2
4
1

24. Now try these
1. 2.
3. 4.
=÷
2
1
3
1
=÷
5
4
2
1
=÷
6
2
4
1
=÷
3
2
4
1
3
2
8
3
8
6
8
5

25. Common denominators
To add or subtract fractions together the
denominator (the bottom bit) must be the
same.
So, sometimes we have to change the
bottoms to make them the same.
In “maths-speak” we say we must get
common denominators

26. Common denominators
To get a common denominator we have to:
1. Multiply the bottoms together.
2. Then multiply the top bit by the correct
number to get an equivalent fraction

27. Common denominators
For example ?
3
1
2
1
=−

28. Common denominators
For example
1. Multiply the bottoms together
?
3
1
2
1
=−
632 =×

29. Common denominators
For example ?
3
1
2
1
=−
2. Write the two fractions as sixths
6
?
2
1
=
6
?
3
1
=

30. Common denominators
For example ?
3
1
2
1
=−
To get ½ into sixths we have multiplied
the bottom (2) by 3. To get an
equivalent fraction we need to multiply
the top by 3 also

31. Common denominators
For example ?
3
1
2
1
=−
To get ½ into sixths we have multiplied
the bottom (2) by 3. To get an
equivalent fraction we need to multiply
the top by 3 also
6
3
6
31
2
1
=
×
=

32. Common denominators
For example ?
3
1
2
1
=−
To get 1/3 into sixths we have multiplied
the bottom (3) by 2. To get an
equivalent fraction we need to multiply
the top by 2 also

33. Common denominators
For example ?
3
1
2
1
=−
To get 1/3 into sixths we have multiplied
the bottom (3) by 2. To get an
equivalent fraction we need to multiply
the top by 2 also
6
2
6
21
3
1
=
×
=

34. Common denominators
For example ?
3
1
2
1
=−
We can now rewrite
=−
3
1
2
1

35. Common denominators
For example ?
3
1
2
1
=−
We can now rewrite
6
2
6
3
3
1
2
1
−=−

36. Common denominators
For example ?
3
1
2
1
=−
We can now rewrite
6
2
6
3
3
1
2
1
−=−
6
23−
=

37. Common denominators
For example ?
3
1
2
1
=−
We can now rewrite
6
2
6
3
3
1
2
1
−=−
6
23−
=
6
1
=

38. Common denominators
This is what we have done:
3
1
2
1
−
1. Multiply the
bottoms
6
?
6
?
−=

39. Common denominators
This is what we have done:
3
1
2
1
−
1. Multiply the
bottoms
6
?
6
?
−=
2.Cross
multiply
6
?
6
31
−
×
=

40. Common denominators
This is what we have done:
3
1
2
1
−
1. Multiply the
bottoms
6
?
6
?
−=
2.Cross
multiply
6
21
6
3 ×
−=
6
?
6
31
−
×
=

41. Common denominators
This is what we have done:
3
1
2
1
−
1. Multiply the
bottoms
6
?
6
?
−=
2.Cross
multiply
6
21
6
3 ×
−=
6
?
6
31
−
×
=
6
2
6
3
−=

42. Now try these
Click on the next slide to reveal the answers.
1. 2.
3. 4.
=+
2
1
3
1
=+
2
1
5
4
=−
6
1
4
3
=+
3
2
4
1
24
14

43. Now try these
1. 2.
3. 4.
=+
2
1
3
1
=+
2
1
5
4
=−
6
1
4
3
=+
3
2
4
1
6
5
12
11
24
14
10
3
12
7
=

44. For further info
Go to:
• BBC Bitesize Maths Revision site
by clicking here: