The Number Line

We can associate each real number with a point on the number line. The location of 0 on the number line is called the origin.

Each point on the number line corresponds to a real number.

For example, on the following number line the point A corresponds to the real number -3 because point A lies 3 units to the left of 0.

The location of a point on the number line is called its coordinate. The coordinate of point A is -3.

To plot a point means to place a dot at the location of the point on the number line.

Example 1

Plot the following numbers on a number line: 9, -8, -4.5, 0, , 2π

Solution

Find the approximate location of each point and place a dot at that point. Recall that π ≈ 3.14, so 2π ≈ 6.28. Also,

Note: The symbol ≈ means "is approximately equal to".