addition and subtraction of fractions

1. 36
??
x4
+7
÷10
x4 ÷6 x3 x5
÷6
x3
÷2
8

2. 29 March 2024
Subtracting Fractions

3. 1
3
−
1
4
=
KNOWLEDGE CHECK
2
3
−
1
5
=
3
4
−
2
5
=

4. 1
3
−
1
4
=
1
12
KNOWLEDGE CHECK
2
3
−
1
5
=
7
15
3
4
−
2
5
=
7
20

5. Josh had
1
2
of a pizza and Tammy took a
1
4
slice.
How much was left?
1
4
1
4
1
2
2
4

6. Sally had
3
4
of a pizza and Ben took a
1
2
slice.
How much was left?
1
2
1
4
3
4
2
4

7. 1
2
To subtract fractions, they must have the same denominator
(they must be split into the same size pieces)
1
4
?
− =
2
4
1
4
If all the denominators are the same, the calculation is easy!

8. 1
3
To subtract fractions, they must have the same denominator
(they must be split into the same size pieces)
1
6
?
− =
2
6
1
6
If all the denominators are the same, the calculation is easy!

9. 1
3
To subtract fractions, they must have the same denominator
(they must be split into the same size pieces)
1
5
?
− =
5
15
2
15
If all the denominators are the same, the calculation is easy!
3
15

10. 4
12
3
12
1
12
=
−
1
3
1
12
=
−
Denominator × 4
Numerator × 4
We need the denominators to be the same.
Which fraction should we change to make the calculation easy?
=
1
4

11. 9
16
2
16
7
16
=
−
3
4
7
16
=
−
Denominator × 4
Numerator × 4
We need the denominators to be the same.
Which fraction should we change to make the calculation easy?
=
1
8

12. Example Complete these calculations in your book.
1) Choose which fraction
you need to change
2) Make an equivalent fraction
3) Subtract the fractions!
1
2
−
1
6
=
2
3
−
1
6
=
1
4
+
1
8
=
2
3
−
2
9
=
3
4
−
5
12
=
5
9
−
1
3
=
3
5
−
7
15
=
2
3
−
1
4
=
4
5
−
2
7
=
(Remember to simplify your answer!)

13. Example Complete these calculations in your book.
1) Choose which fraction
you need to change
2) Make an equivalent fraction
3) Subtract the fractions!
1
2
−
1
6
=
2
6
=
1
3
2
3
−
1
6
=
3
6
=
1
2
1
4
+
1
8
=
1
8
2
3
−
2
9
=
4
9
3
4
−
5
12
=
4
12
=
1
3
5
9
−
1
3
=
2
9
3
5
−
7
15
=
2
15
2
3
−
1
4
=
5
12
4
5
−
2
7
=
18
35
(Remember to simplify your answer!)
Answers

14. Example Complete these calculations in your book.
1) Choose which fraction
you need to change
2) Make an equivalent fraction
2
3
−
4
9
=
3
4
+
3
16
=
1
2
−
3
10
=
2
3
−
1
2
=
2
3
−
3
5
=
3
4
−
3
5
=
5
6
−
1
4
=
5
9
−
2
5
=
3
7
8
− 1
2
3
=
(Remember to simplify your answer!)
3) Subtract the fractions!

15. Example Complete these calculations in your book.
1) Choose which fraction
you need to change
2) Make an equivalent fraction
2
3
−
4
9
=
2
9
3
4
−
3
16
=
9
16
1
2
−
3
10
=
2
10
=
1
5
2
3
−
1
2
=
1
6
2
3
−
3
5
=
1
15
3
4
−
3
5
=
3
20
5
6
−
1
4
=
14
24
=
7
12
5
9
−
2
5
=
7
45
3
7
8
− 1
2
3
= 2
5
24
(Remember to simplify your answer!)
3) Subtract the fractions!
Answers

16. 3
6
2
6
− =
1
6
Numerator
& Denominator
× 3
Numerator
& Denominator
× 2
What common denominator could we use?
1
2
1
3
=
−
When we add or subtract fractions we must have a
common denominator.

17. 18
30
5
30
− =
13
30
Numerator
& Denominator
× 6
Numerator
& Denominator
× 5
What common denominator could we use?
3
5
1
6
=
−
When we add or subtract fractions we must have a
common denominator.

18. 15
18
8
18
− =
7
18
Numerator
& Denominator
× 3
Numerator
& Denominator
× 2
What common denominator could we use?
5
6
4
9
=
−
When we add or subtract fractions we must have a
common denominator.

20. 3
6
2
6
− =
1
6
Numerator
& Denominator
× 3
Numerator
& Denominator
× 2
1
2
1
3
=
−
EXAMPLE
What common denominator
could we use?

21. 9
12
4
12
− =
5
12
Numerator
& Denominator
× 3
Numerator
& Denominator
× 4
3
4
1
3
=
−
EXAMPLE
What common denominator
could we use?

22. 15
20
8
20
− =
7
20
Numerator
& Denominator
× 5
Numerator
& Denominator
× 4
3
4
2
5
=
−
EXAMPLE
What common denominator
could we use?

23. 25
30
18
30
− =
7
30
Numerator
& Denominator
× 5
Numerator
& Denominator
× 6
5
6
3
5
=
−
EXAMPLE
What common denominator
could we use?

24. 14
18
9
18
− =
5
18
Numerator
& Denominator
× 2
Numerator
& Denominator
× 3
7
9
3
6
=
−
EXAMPLE
What common denominator
could we use?

25. 21
24
9
24
− =
12
24
Numerator
& Denominator
× 3
Numerator
& Denominator
× 2
7
8
3
12
=
−
EXAMPLE
What common denominator
could we use?
=
1
2

26. 1
3
−
1
4
=
EXAMPLE
1
4
−
1
5
=
2
3
−
2
5
=
4
5
−
1
6
=
6
7
−
3
5
=
4
5
+
3
8
=

27. 1
3
−
1
4
=
1
12
EXAMPLE
1
4
−
1
5
=
1
20
2
3
−
2
5
=
4
15
4
5
−
1
6
=
19
30
6
7
−
3
5
=
9
35
4
5
−
3
8
=
17
40
Answers

28. You are only allowed to use the numbers 2, 3, 4 and 5
What is the largest
addition total
you can make?
What is the smallest
subtraction total
you can make?

29. You are only allowed to use the numbers 2, 3, 4 and 5
What is the largest
addition total
you can make?
What is the smallest
subtraction total
you can make?
5
2
4
3
2
3
4
5
3
5
6
−
2
15

30. I can subtract fractions with the same
denominator.
I can subtract fractions with different
denominators.
I can subtract mixed numbers.
Check your success!

31. I can subtract fractions with the same
denominator.
I can subtract fractions with different
denominators.
I can subtract mixed numbers.
Check your success!

32. Write a text message to a friend describing…
How to subtract
fractions that have
different
denominators.