Elevise
  • Home
  • GCSE Maths
  • GCSE Science
  • Membership
Back to Edexcel Number (F) Home
1.1 L) Subtracting & Adding Negative Numbers
Here are the rules when two signs are next to one another:
Picture
From these rules, we can see that two signs of the same result in addition; this is the case for + + and - -. Also, opposite signs result in subtraction; this was the case for - + and + -.  
 
Let’s have a few examples.

Example 1 
Complete the calculation:
Picture
We are taking away a negative number, which means that we are adding 3. 
Picture
​The answer to this question is 11. 

Example 2 
Complete the calculation:
Picture
We are adding a negative number. Opposite signs result in a negative sign. The calculation becomes:
Picture
​The answer is 15. 

Example 3 
Complete the calculation:
Picture
We are adding a positive and we know that signs that are the same become a positive. Therefore, the calculation becomes:
Picture
​Therefore, the answer to this question is 78. 

Example 4 
Complete the calculation:
Picture
We are taking a positive and as the signs are opposite, it results in a negative. The calculation is:
Picture
The start number is a negative (-24). Therefore, it is probably best to sketch a quick number line with -24 on it. My sketch is given below.
Picture
We are taking 4 away, which means that we are moving 4 towards the left. 
Picture
​The answer for this calculation is -28. 

End Note
The key rules to remember from this section is that:
  • Two of the same signs result in addition; this is the case for + + and - -
  • Opposite signs result in subtraction; this was the case for - + and + -
 
It is worth getting these rules down on a revision card. 
Home
GCSE Maths
GCSE Science
Membership
UNITED KINGDOM
INFO@ELEVISE.CO.UK
  • Home
  • GCSE Maths
  • GCSE Science
  • Membership