Skill: Interpret line plots

A line plot shows measurement data on a number line.

• Each X stands for one measurement.
• Count the Xs above a value to find how many times that measurement occurred.
• Look carefully at the scale. The marks may increase by whole numbers, $\frac{1}{2}$, or $\frac{1}{4}$.

Example

A class measured pencil lengths to the nearest $\frac{1}{4}$ inch.

Length	$1$ inch	$1\frac{1}{4}$ inches	$1\frac{1}{2}$ inches	$1\frac{3}{4}$ inches	$2$ inches
Xs	XX	XXX	X	XX	X

Question: How many pencils were measured altogether, and how many more pencils were $1\frac{1}{4}$ inches long than $1\frac{3}{4}$ inches long?

Step 1: Count all the Xs.

$$2+3+1+2+1=9$$

So, 9 pencils were measured.

Step 2: Compare the two groups.

• There are $3$ Xs above $1\frac{1}{4}$ inches.
• There are $2$ Xs above $1\frac{3}{4}$ inches.

Find the difference:

$$3-2=1$$

So, there was 1 more pencil measuring $1\frac{1}{4}$ inches.

Always count the Xs, not just the number of marked values.