What are Negative Numbers?
A negative number is a number less than zero.
Negative numbers are written with a minus sign in front, like this:
They can be also written as minus 9 or negative 9, these both mean the same thing: -9.
This number line shows the numbers counting up from zero:
You need to know that there are numbers below zero. They are the negative numbers. Here is the number line also showing the negative numbers:
Ordering Negative Numbers
Ordering negative numbers is easy but remember negative numbers get lower in value as the numbers progress… so -4 has a lower value than -1.
Moving from zero down the number line, you can see that -4 is a smaller number than -1. This can seem strange at first as 4 is a bigger number than 1. However remember these are negative numbers and -4 is smaller than -1, just look at it’s position on the number line. When asked to place negative numbers in order it is important to remember this.
Question: Place the following numbers in order of size:
-2, 4, -6, 1, 5
We must first remember the number line, you can quickly draw one out if you need to and then look at the position of the numbers you are comparing:
From the diagram we can see the order of size:
-6, -2, 1, 4, 5
Adding or Subtracting Negative Numbers
When adding or subtracting negative numbers always draw a number line
Move up the number line when adding on numbers and move down the line when subtracting. It is worth remembering that the number line we draw is only a part of the line, it can go on for ever in both directions.
Take a look at the sum below:
5 minus 8 = -3
If we draw a number line and then work our way back from 5 by 8 numbers we can see the result -3:
Questions about temperature often involve negative numbers.
A common use of negative numbers is when we look at a thermometer and see negative temperatures. The temperatures below zero are the negative numbers.
For example -2°C is a temperature two degrees below zero.
°C means degrees Celcius and this is a unit of measuring temperature.
When asked to add or subtract negative temperatures you can draw a number line and use the method of adding or subtracting negative numbers – don’t be put off by the °C symbol, the numbers can be treated like any other number.