Explanation
In this lesson, we learn how to plot points on a number line.
A number line is a straight line with numbers placed in order.
It extends forever in both directions:
\(\dots, −3, −2, −1, 0, 1, 2, 3, \dots\)
A number line is \(1D\), which means one-dimensional.
In \(1D\), we only need one value to locate a point.
For example:
\(P = 4\)
means the point is located at \(4\) on the number line.
The point can be:
• a positive number
• a negative number
• zero
• a fraction
• a decimal
For example:
\(4, −5, 0, 1/2, −2 1/4, 1.5\)
All of these can be plotted on a number line.
The number line can be drawn horizontally, vertically, or even diagonally. The direction does not change the main idea.
As long as the points lie on one straight line and each point needs only one value, it is still \(1D\).
Formula / Rule
In \(1D\), a point needs only one coordinate:
\(P = x\)
where:
\(x\) is the position of the point on the number line.
A simple rule is:
positive numbers are usually plotted to the right of \(0\).
negative numbers are usually plotted to the left of \(0\).
\(0\) is the origin.
Fractions and decimals are plotted between whole numbers.
Examples
Plot the following points on a number line:
\(P_1 = 4\)
\(P_2 = −5\)
\(P_3 = 0\)
\(P_4 = \frac{1}{2}\)
\(P_5 = −2 \frac{1}{4}\)
\(P_6 = 1.5\)
Point \(P_1\)
\(P_1 = 4\)
This point is \(4\) units to the right of \(0\).
Point \(P_2\)
\(P_2 = −5\)
This point is \(5\) units to the left of \(0\).
Point \(P_3\)
\(P_3 = 0\)
This point is at the origin.
Point \(P_4\)
\(P_4 = \frac{1}{2}\)
This point is halfway between \(0\) and \(1\).
Point \(P_5\)
\(P₅ = −2 \frac{1}{4}\)
This point is between \(−2\) and \(−3\), closer to \(−2\).
Point \(P_6\)
\(P_6 = 1.5\)
This point is halfway between \(1\) and \(2\).
So, to plot points in \(1D\), we only need one value for each point.
Video Explanation
Practice
Continue Learning
- Plotting Points on a Number Line (\(1D\)) (Current lesson)
- Distance Formula in \(1D\)
- Distance between Two Points in \(1D\)