Skill: Interpret line graphs

To interpret a line graph, read the graph in an organized way:

1. Read the horizontal axis to see what is being measured across an order, such as days or months.
2. Read the vertical axis to see the quantity being measured.
3. Check the scale on the vertical axis. Make sure you know how much each interval represents.
4. Read the plotted points to find exact values.
5. Look at the connecting segments:
   • A segment going up shows an increase.
   • A segment going down shows a decrease.
   • A flat segment shows no change.
6. Identify the highest value, lowest value, and overall trend.

Example

A line graph shows the number of pages Maya read each day.

• The horizontal axis is labeled Day and shows Monday through Friday.
• The vertical axis is labeled Pages Read and is marked in intervals of $1$.
• The plotted points are:

Day	Pages read
Monday	$2$
Tuesday	$2$
Wednesday	$5$
Thursday	$4$
Friday	$4$

Question: Interpret the graph.

Step 1: Find an exact value.
On Wednesday, the point is at $5$. Maya read

$$5\text{ pages}.$$

Step 2: Find an increase.
The line rises from Tuesday to Wednesday. The number of pages increased from $2$ to $5$.

$$5-2=3$$

Maya read $3$ more pages on Wednesday than on Tuesday.

Step 3: Find a constant interval.
The points for Monday and Tuesday are both at $2$. The line is flat between them, so the number of pages stayed constant.

Step 4: Find the highest and lowest values.
The highest point is Wednesday at $5$ pages. The lowest value is $2$ pages, which occurred on Monday and Tuesday.

Step 5: Describe the overall trend.
The graph rises from Monday to Wednesday, then falls slightly on Thursday and stays the same on Friday. Overall, Maya read more pages at the end of the week than at the beginning.

Remember: the connecting lines help show whether the values increase, decrease, or stay constant between plotted observations. They do not automatically give measured values for every point between the observations.