Unit 7: Numeracy skills
Fractions
Multiplication of fractions
It may help to understand multiplication if you interpret the ‘x’ sign as ‘of’. So:
1 |
x |
2 |
means |
1 |
of |
2 |
= |
1 |
- |
|
- |
|
- |
|
- |
|
- |
2 |
|
5 |
|
2 |
|
5 |
|
5 |
The calculation involves multiplying both numerators and both denominators then cancelling down. For example:
1 |
x |
2 |
= |
1 x 2 |
= |
2 |
1 |
= |
1 |
|
|
|
|
|
|
|
- |
|
- |
------- |
-------- |
|
- |
|
|
|
|
|
|
2 |
|
5 |
|
2 x 5 |
|
10 |
5 |
|
5 |
|
|
|
|
|
|
|
4 |
x |
2 |
= |
4 x 2 |
= |
|
8 |
and |
|
7 |
x |
3 |
= |
7 x 3 |
= |
21 |
|
|
|
|
|
- |
|
- |
------- |
------ |
---- |
|
- |
-------- |
|
--- |
|
|
|
|
5 |
|
3 |
|
5 x 3 |
|
1 |
5 |
|
1 |
1 |
|
8 |
|
11 x 8 |
|
88 |
|
|
|
|
|
When multiplying, you can cancel down during the sum as well as at the final stage – it often makes the calculation easier. For example:
3 |
1 |
x |
|
3 |
= |
1 |
|
x |
3 |
1 |
= |
1 |
x |
1 |
= |
1 |
----- |
|
----- |
------ |
|
---- |
|
- |
|
- |
|
- |
|
9 |
|
8 |
2 |
|
9 |
3 |
|
|
2 |
|
3 |
|
2 |
|
6 |
|
|
5 |
x |
6 |
1 |
= |
5 x 1 |
= |
|
5 |
|
|
|
|
|
|
------- |
----- |
|
------ |
|
----- |
|
|
|
|
|
2 |
4 |
4 |
|
|
7 |
|
4 x 7 |
|
2 |
8 |
|
|
|
|
|
|

SMILE - Numeracy skills by Tom Frank, Eric Williams and Clare Wright, University of Birmingham Careers Centre adapted by Marion Kelt Glasgow Caledonian University is licensed under a Creative Commons Attribution 3.0 Unported License.