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Unit 7: Numeracy skills

Fractions

Subtracting fractions

This works in the same way as addition. If the denominators are the same, simply subtract along the top line:

5 - 3 = 5 - 3 = 2 = 1 x 2 = 1        
-   - -------   -   ------   -      
6   6     6     6   3 x 2   3        

12 - 1 = 12 - 3 x 1 = 12 -   3 = 1 2 - 3 =   9
---   - --- ------   --- ----   ------------   -----
15   5   15   3 x 5   15   1 5     1 5     1 5

Cancelling down gives:

  9 = 3 x 3 = 3
----   ------   -
1 5   3 x 5   5

An alternative method would have been to cancel down 12 / 15 to 4 / 5 initially leaving an easier sum 4 / 51 / 5 = 3 / 5

Creative Commons License
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.