fraction rules
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Mr. Standring Math
FractionsSuper-ultra-mega solving skills ;)
Mr. Standring Math
This presentation will help you to: add subtract multiply and divide fractions
Fractions
Mr. Standring Math
To add fractions together the denominator (the bottom bit) must be the same.
Example
Adding fractions
8
2
8
1
Mr. Standring Math
To add fractions together the denominator (the bottom bit) must be the same.
Example
Adding fractions
8
2
8
1
8
21
Mr. Standring Math
To add fractions together the denominator (the bottom bit) must be the same.
Example
Adding fractions
8
2
8
1
8
21
8
3
Mr. Standring Math
Click to see the next slide to reveal the answers.
1. 2.
3. 4.
Now try these
3
1
3
1
12
7
12
3
7
4
7
2
4
1
4
2
Mr. Standring Math
1. 2.
3. 4.
Now try these
3
1
3
1
12
7
12
3
7
4
7
2
4
1
4
2
3
24
3
7
6
12
10
Mr. Standring Math
Subtracting fractions
8
2
8
3
To subtract fractions the denominator (the bottom bit) must be the same.
Example
Mr. Standring Math
Subtracting fractions
8
2
8
3
8
23
To subtract fractions the denominator (the bottom bit) must be the same.
Example
Mr. Standring Math
Subtracting fractions
8
2
8
3
8
23
8
1
To subtract fractions the denominator (the bottom bit) must be the same.
Example
Mr. Standring Math
Now try these
Click on the next slide to reveal the answers.
1. 2.
3. 4.
3
1
3
2
12
3
12
77
3
7
4
4
1
4
2
Mr. Standring Math
Now try these
.
1. 2.
3. 4.
3
1
3
2
12
3
12
77
3
7
4
4
1
4
2
3
14
1
7
1
12
4
Mr. Standring Math
Multiplying fractions
To multiply fractions we multiply the tops and multiply the bottoms
Top x Top
Bottom x Bottom
Mr. Standring Math
Multiplying fractions
Example
3
1
2
1
Mr. Standring Math
Multiplying fractions
Example
3
1
2
1
32
11
Mr. Standring Math
Multiplying fractions
Example
3
1
2
1
32
11
6
1
Mr. Standring Math
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
Mr. Standring Math
Now try these
.
1. 2.
3. 4.
3
1
3
1
5
3
3
1
5
4
4
2
4
1
4
29
116
2
20
8
15
3
Mr. Standring Math
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!
Mr. Standring Math
Dividing fractions
• Turn the second fraction upside down
Example ?3
1
6
1
1
3
6
1
Mr. Standring Math
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
Mr. Standring Math
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
Mr. Standring Math
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
Mr. Standring Math
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
Mr. Standring Math
Now try these
1. 2.
3. 4.
2
1
3
1
5
4
2
1
6
2
4
1
3
2
4
1
3
28
3
8
6
8
5
Mr. Standring Math
To add or subtract fractions together the denominator (the bottom bit) must be the same.
Common denominators
So, sometimes we have to change the bottoms to make them the same.
In “maths-speak” we say we must get common denominators
Mr. Standring Math
To get a common denominator we have to:
Common denominators
1. Multiply the bottoms together.
2. Then multiply the top bit by the correct number to get an equivalent fraction
Mr. Standring Math
For example
Common denominators
?3
1
2
1
Mr. Standring Math
For example
Common denominators
1. Multiply the bottoms together
?3
1
2
1
632
Mr. Standring Math
For example
Common denominators
?3
1
2
1
2. Write the two fractions as sixths
6
?
2
1
6
?
3
1
Mr. Standring Math
For example
Common denominators
?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
Mr. Standring Math
For example
Common denominators
?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
Mr. Standring Math
For example
Common denominators
?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
Mr. Standring Math
For example
Common denominators
?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
Mr. Standring Math
For example
Common denominators
?3
1
2
1
We can now rewrite
3
1
2
1
Mr. Standring Math
For example
Common denominators
?3
1
2
1
We can now rewrite
6
2
6
3
3
1
2
1
Mr. Standring Math
For example
Common denominators
?3
1
2
1
We can now rewrite
6
2
6
3
3
1
2
1
6
23
Mr. Standring Math
For example
Common denominators
?3
1
2
1
We can now rewrite
6
2
6
3
3
1
2
1
6
23
6
1
Mr. Standring Math
Common denominators
This is what we have done:
3
1
2
1
1. Multiply the bottoms
6
?
6
?
Mr. Standring Math
Common denominators
This is what we have done:
3
1
2
1
1. Multiply the bottoms
6
?
6
?
2.Cross multiply
6
?
6
31
Mr. Standring Math
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
Mr. Standring Math
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
Mr. Standring Math
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
Mr. Standring Math
Now try these
1. 2.
3. 4.
2
1
3
1
2
1
5
4
6
1
4
3
3
2
4
1
6
512
11
24
1410
3
12
7
Mr. Standring Math
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