Starting at 0 we can count up in units like this:

 

0    1    2    3    4    5    6    7 ...

 

But what happens before zero?

 

We have the negative numbers, like this:

  -7    -6    -5    -4    -3    -2    -1    0

 

If we count up, we move from the left to the right and the numbers increase. 

So, -7 to -6 is moving from the left to the right and the numbers have increased because -6 is bigger than -7.

 

If we count back, we move from the right to the left and the numbers decrease.

So, -3 to -4 is moving from the right to the left and the numbers have decreased because -4 is smaller than -3.

 

Here is part of a number line going from 7 down to -7:

 

 

-7   - 6    -5    -4    -3    -2    -1    0      1    2    3    4    5    6    7 

 

 

Example

Count back to work out the missing number.

 

 -4    -3        -1    0    1    2    3

 

What is the missing number?

 

 

 

Answer

Counting back from 0 means the numbers decrease.   

-3    -2    -1    0 

 

So the missing number is -2.

 

Does that make sense?