Algebra 1 Common Core Student Edition, Grade 8-9

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Li n e Gr ap h s

Line graphs are u sed to display th e change in a set of d ata over a p erio d of time.

A m ultiple-line graph shows change in m ore th a n one category of d ata over time.

You can use a line graph to look for trends an d m ake predictions.

Ex a m p l e

The data in the table below show the num ber of households, in thousands, that

have cable TV and the num ber o f household s that subscribe to new spapers in a

certain city. Graph the data.

Households W ith Cable TV and Newspapers (thousands)

Year 1980 1990 1995 2000 2005

Cable TV 15.2 51.9 60.5 68.6 73.9

Newspapers 62.2 62.3 58.2 55.8 53.3

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Since the data show changes over tim e for two sets of data, use a d ouble line

graph. The horizontal scale displays years. The vertical axis shows th e n u m b e r of

households for each category.

Households W ith

Cable TV and Newspapers

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■Cable TV

■Newspaper

1980 1990

Year

2000 2010

Notice that there is a break in the vertical axis. You can use a zigzag line to indicate a

break from 0 to 15 since there is no data less th a n 15 to graph.

Ex e r c i se s

Graph the data in each table.

1. M a r k e t S h a r e ( p e r c e n t )

Year^2004200520062007

Rap/Hip Hop 12.1 13.3 11.4 10.8

Pop 10.0 8.1 7.1 1 0. 7

so u r c e: Record ing Ind ust ry o f Am erica

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PowerAlgebra.com

2. Percent o f Schools W ith In tern et Access

Year 1997 1999 2001 2003

Elementary 75 94 99 100

Secondary 89 98 100 100

so u r c e: National Center for Education Statistics

Sk i l l s H a n d b o o k 811