In this section we look at adding and subtracting when negative numbers are involved.
We will use a number line like the one below to help us.
If you subtract a positive number you move to the left on a number line. Always start from the position of the first number.  
3 + 5 = 8 (start at 3 and move 5 to the right) 4 + 5 = 1 (start at 4 and move 5 to the right) 9 + 5 = 4 (start at 9 and move 5 to the right)  9  7 = 2 (start at 9 and move 7 to the left) 3  7 = 4 (start at 3 and move 7 to the left) 1  7 = 8 (start at 1 and move 7 to the left) 
Practice Questions
Work out the answer to each of these questions then click on the button marked
to see whether you are correct.
(a) 3 + 8  
(b) 8 + 5  
(c) 5  7  
(d) 2  3 
We can also use a number line when adding or subtracting negative numbers.
If you subtract a negative number you move to the right on a number line. Again, start the movement from the position of the first number.  
7 + (4) = 3 (start at 7 and move 4 to the left) 1 + (4) = 3 (start at 1 and move 4 to the left) 3 + (4) = 7 (start at 3 and move 4 to the left)  4  (3) = 7 (start at 4 and move 3 to the right) 2  (3) = 1 (start at 2 and move 3 to the right) 8  (3) = 5 (start at 8 and move 3 to the right) 
Practice Questions
Work out the answer to each of these questions then click on the button marked
to see whether you are correct.
(a) 4 + (2)  
(b) 1 + (3)  
(c) 4  (2)  
(d) 5  (3) 
This table may help you remember the rules:
Adding a positive  move right  Subtracting a positive  move left 
Adding a negative  move left  Subtracting a negative  move right 
you start with a positive or negative number 
