Skill: Interpret simple line graphs

A line graph shows how a measured amount changes across an ordered sequence, such as days.

To read one:

1. Look at the horizontal axis. It tells what is being measured in order, such as days.
2. Look at the vertical axis. It tells the amount.
3. Check the scale. Count how much each interval represents.
4. Find a point above each item on the horizontal axis.
5. Read the point across to the vertical axis.
6. Compare the values to describe increases, decreases, greatest values, least values, or differences.

Worked example

A line graph shows the number of books Maya read from Monday to Friday. The vertical axis is labeled “Books” and is marked in intervals of $1$.

The plotted points are:

• Monday: $2$ books
• Tuesday: $4$ books
• Wednesday: $3$ books
• Thursday: $5$ books
• Friday: $4$ books

Question: How did the number of books change during the week?

Step 1: Read each point.

Move up from each day to its point, then across to the vertical axis:

• Monday is $2$.
• Tuesday is $4$.
• Wednesday is $3$.
• Thursday is $5$.
• Friday is $4$.

Step 2: Describe increases and decreases.

• From Monday to Tuesday, the number increased from $2$ to $4$.
• From Tuesday to Wednesday, it decreased from $4$ to $3$.
• From Wednesday to Thursday, it increased from $3$ to $5$.
• From Thursday to Friday, it decreased from $5$ to $4$.

Step 3: Find the greatest and least values.

• The greatest value is $5$ books on Thursday.
• The least value is $2$ books on Monday.

Step 4: Find a difference.

The difference between Thursday and Monday is

$$5-2=3.$$

So, Maya read $3$ more books on Thursday than on Monday.

The segments connecting the points help show the change from one day to the next. They do not mean Maya read every number between the two plotted days; the measured values are the points for Monday, Tuesday, Wednesday, Thursday, and Friday.