Understand and use formulae in KS3 algebra. Substitute values, rearrange to change the subject, and check results with sensible units in real-life contexts.
														
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You can find more about this topic by visiting  BBC Bitesize - Expressions and formulae
														
 Either can be used 
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 We call them variables because their values vary  
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 Remember that all formulae contain an equals sign 
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 2b = 2 x 4.  We have been told that a = 2b and therefore a must be 8 
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 30 - 2 = c.  Sometimes you have to work backwards in order to find the answer 
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 If a = 3 then a 2 = 9. 25 - 9 = 16 so b 2 = 16, therefore b must = 4 
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 In this case you have two variables (a and b) and there is no reason why they cannot both have the same value - in this case 6 
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 Don't worry, you will NOT normally be presented with formulae that don't add up! 
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 Perimeter means 'all the way around the outside' 
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 If m is the number of miles travelled in one hour then the miles covered in 4 hours would be 4 x m or 4m 
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