Zero is included on the integer number line. The positive numbers are to the right of zero and the negative numbers are to the left of zero. The number zero itself is neither positive nor negative.
The fi rst number on the left side of zero is –1, then –2, –3 and so on as you move further away from 0. This is because the numbers are decreasing in size. For example, –5 is less than –1.
A real-life example of this can be seen in multi-storey car parks. The fl oor on –3 is lower than the fl oor on –1. Furthermore, a temperature a reading of –20°C is lower than a temperature of –10°C.
Adding and subtracting integers (ℤ) on the number line
Addition –3 + 5 = 2
Move 5 steps to the right ➞
–6 –5 –4 –3 –2 –1 0 1 2 3 4 5 6 START
STOP Natural numbers vs integers
This table will help you to understand the diff erences and similarities between natural numbers and integers.
Subtraction –2 – 4 = –6
Move 4 steps to the left
STOP –6 –5 –4 –3 –2 –1 0 1 2 3 4
START
Negative (decreasing)
Integer number line Negative integers –4 –3 –2 –1 Positive integers 0 1 2 3 4 Zero is neither positive nor negative
Positive (increasing)
4 3 2 1 0
–1 –2 –3 –4
Adding and subtracting integers (ℤ) on the number line is done exactly the same way as adding or subtracting natural numbers (ℕ) on the number line.
Number lines do not have to be horizontal, they can also be vertical. In this case, we move up for positive (increasing) and down for negative (decreasing).
Natural numbers
Whole numbers Positive
Integers Whole numbers Positive and negative
Does NOT include zero DOES include zero Symbol ℕ
Symbol ℤ
How to draw a number line Use a ruler to draw a straight line.
1 2 Divide the line into equal sections. –4 3 –3 –2 –1 0 1 2 3 4
Insert the numbers. Numbers moving to the right are positive and increasing, numbers moving to the left are negative and decreasing.
4 3 2 1 0
–1 –2 –3 –4
You can also draw a vertical number line using the same method.