1. EXAMPLE 1
Interpreting a Bar Graph
Volcanoes
The bar graph at the right shows the number of historically active volcanoes in four countries. Which country has the most historically active volcanoes?

2. EXAMPLE 1
Interpreting a Bar Graph
Use the bar graph above about volcanoes. Answer the question or explain why you can’t answer the question using the graph.
a. Which country has the most historically active volcanoes?
b. Which country has the most volcanic eruptions in a given year?

3. EXAMPLE 1
Interpreting a Bar Graph
SOLUTION
a. The vertical axis in the bar graph is labeled Historically active volcanoes, so the tallest bar represents the country with the most historically active volcanoes. Because the United States has the tallest bar, it has the most historically active volcanoes.
b. Having more historically active volcanoes doesn’t necessarily mean having more eruptions, so you can’t answer this question from the bar graph.

4. GUIDED PRACTICE
for Example 1
Use the bar graph above about historically active volcanoes.
1. About how many more historically active volcanoes does Chile have than Mexico?
ANSWER
About 80 volcanoes

5. GUIDED PRACTICE
for Example 1
Use the bar graph above about historically active volcanoes.
2. Which country has the least number of historically active volcanoes?
ANSWER
Canada

6. GUIDED PRACTICE
for Example 1
Use the bar graph above about historically active volcanoes.
3. About how many historically active volcanoes do Canada, Mexico, and the U.S. have altogether?
ANSWER
215 volcanoes

7. EXAMPLE 2
Making a Frequency Table
Roller Coasters
The data show the heights, in meters, of some of the tallest roller coasters in the world. Make a frequency table of the data.
66.4, 94.5, 68.3, 115, 62.5, 97, 66.4, 126.5, 63.4, 74.7, 63.4, 70.1, 66.4, 64.9, 63.7, 79, 63.4, 63.1, 62.5, 61.9, 71.6

8. EXAMPLE 2
Making a Frequency Table
SOLUTION
STEP 1
Choose intervals of equal size for the data. The intervals should include numbers from 61.9 to
STEP 2
Tally the data in each interval. Use tally marks to record each occurrence of a height in its interval.
STEP 3
Write the frequency for each interval by totaling the tally marks.

9. EXAMPLE 2
Making a Frequency Table

10. EXAMPLE 3
Making a Histogram
Make a histogram of the data in the frequency table above.
STEP 1
Draw and label the horizontal and vertical axes. Start the vertical scale at 0 and end at a point greater than 13. Use equal increments.
STEP 2
Draw a bar to represent the frequency of each interval. The bars of neighboring intervals should touch.
STEP 3
Write a title for the histogram.

11. EXAMPLE 3
Making a Histogram

12. GUIDED PRACTICE
for Examples 2 and 3 4.
Using the data from Example 2, make a new frequency table using 6 intervals. Then make a histogram from your frequency table.
What If?
SOLUTION