Line Graphs

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1-7
Line Graphs
Warm Up
Problem of the Day
Lesson Presentation
Course 2
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Warm Up 1. What is the x-coordinate of the point
(2, 3)? 2. To plot the point (3, 7) you would
move right ___ units then up ___ units. 3. To
plot the point (4, 5) would you move left or
right first?
2
3
7
right
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Problem of the Day Find three mistakes on the
graph shown.
The line does not connect all the sales.
Trucks Sold
The intervals on the vertical scale are not equal.
Number of trucks sold
The data for Tuesday shows sales of 6.5 trucks.
Mon Tues Wed Thurs Fri
Days of week
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Learn to display and analyze data in line graphs.
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Vocabulary
line graph double-line graph
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You can use a line graph to show how data changes
over a period of time.
A line graph uses line segments to connect data
points. The result is a visual record of change.
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Additional Example 1 Making a Line Graph
Make a line graph of the data in the table. Use
the graph to determine during which 2-hour period
did the temperature change the most?
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Additional Example 1 Continued
95 F 90 F 85 F 80 F 75 F
11 AM 1 PM 3 PM 5 PM
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Additional Example 1 Continued
Step 2 Plot a point for each pair of values.
Connect the points using line segments.
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Additional Example 1 Continued
Step 3 Label the axes and give the graph a
title.
Temperatures on a Given Day
Temperature F
Time
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Additional Example 1 Continued
The temperature changed the most between 11 A.M.
and 1 P.M.
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Try This Example 1
Step 1 Determine the scale and interval for each
axis.
25 20 15 10 5
Jan Feb Mar Apr
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Try This Continued
Step 2 Plot a point for each pair of values.
Connect the points using line segments.
25 20 15 10 5
Jan Feb Mar Apr
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Try This Continued
Step 3 Label the axes and give the graph a title.
Homes Sold
25 20 15 10 5
Number of Homes Sold
Jan Feb Mar Apr
Month
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Try This Continued
March showed the greatest increase in number of
homes sold.
Homes Sold
25 20 15 10 5
Number of Homes Sold
Jan Feb Mar Apr
Month
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You can use a line graph to estimate values
between data points.
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Additional Example 2
Using a Line Graph to Estimate
Data
Use the graph to estimate the population of
Florida in 1950.
To estimate the population in 1950, find the
point on the line between 1940 and 1960 that
corresponds to 1950.
The graph shows about 3.5 million people.
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Try This Example 2
Use the graph to estimate the population of
Florida in 1970.
To estimate the population in 1970, find the
point on the line between 1960 and 1980 that
corresponds to 1970.
The graph shows about 7.5 million people.
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A double-line graph shows change over time for
two sets of data.
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Additional Example 3 Making a Double-Line Graph
The table shows stock prices for two stocks in
one week. Make a double-line graph of the data.
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Additional Example 3 Making a Double-Line Graph
Stock Prices
Plot a point for Stock A for each day of the
week.
Price ()
Then, using a different color, plot a point for
Stock B for each day of the week.
Day
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Additional Example 3 Continued
Stock Prices
Connect the points.
Price ()
Day
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Additional Example 3 Continued
Stock Prices
Make a key to show what each line represents.
Price ()
Day
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Try This Example 3
Stock Prices
Plot a point for Stock A for each day of the
week.
Price ()
Then, using a different color, plot a point for
Stock B for each day of the week.
Day
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Try This Example 3
Stock Prices
Connect the points.
Price ()
Day
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Try This Example 3
Stock Prices
Make a key to show what each line represents.
Price ()
Day
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Lesson Quiz
Make a double line graph of the data.
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Lesson Quiz
Hot Air Balloon Height
400 350 300 250 200 150 100 50 0
Height
Balloon 1
Balloon 2
600 615 630 645 700 715
Time (A.M.)