Number Lines

1) The Number Line explained

In mathematics, a number line is a picture of a straight line on which every point corresponds to a real number, and every real number to a point. Often the integers are shown as specially-marked points evenly spaced on the line. Although this image only shows the integers from -9 to 9, the line includes all real numbers (including values that lie between the marked integers). This line continues "forever" in each direction. It is often used as an aid in teaching simple addition and subtraction, especially involving negative numbers.

2) Work Backwards from points in the answers

Often the question will ask you to identify the number line that corresponds to a given equation. Rather than generate the correct number line from scratch, select points from the answer's choices and determine if they satisfy the equation. If they do not work in the equation, then that choice is wrong.

3) Filled versus Not-Filled endpoints

Equations that include the terms "Greater Than or Equal To" ( ≥ ) or "Less Than or Equal To" ( ≤ ) correspond to number lines with the endpoints filled in. The number line below represents the solution to x ≤ 2.5

Equations containing "greater than" ( > ) or "less than" ( < ) correspond to number lines with the end points circled. The number line below represents the solution to x < 2.5.