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A number line is a line on which numbers are represented in ascending order.
This number line can be extended to the left to represent numbers which
are smaller than 0. Such numbers are called negative numbers.
For example, –1 (called negative one or minus one) is positioned 1 unit
to the left of 0. So, –1 is less than zero.
Similarly, –2 (called negative two or minus two) is 2 less than zero
and –3 (called negative
three or minus three) is 3 less than zero
and so on.
From the preceding discussion we can define the number line as follows:
A line on which the numbers on both sides of zero are represented is said
to be a number line.
Positive numbers are represented on the right of the zero and negative
numbers are represented on the left of the zero as shown in the above
diagram.
Example 1
Write down the elevation information of the following places on a number
line. Use the minus sign (–) to represent elevation below sea level.
a. Mt. Kosciusko (Australia) 2230 m above
sea level
b. Bangalore (India) 1000 m above sea
level
c. Death Valley (USA) 85 m below sea level
d. Qattara Depression (Egypt) 392 m below sea level
Solution:
Example 2
Write down the temperature information for the following places on a
number line and use the minus sign (–) to indicate any temperature that is
below zero.
a. Toronto (Canada) –14ºC
b. Melbourne (Australia) 30ºC
c. London (UK) –6ºC
d. New Delhi (India) 20ºC
Solution:
For the remainder of this chapter, we will restrict our discussion to
positive numbers only. Negative numbers will be re-introduced in Year
8.
Key Terms
number line, negative
numbers
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