Page 186 - MAT KS3 Y8 Cambridge CheckPoint

18.3 Interpreting and drawing line graphs

18.3 Interpreting and drawing line graphs

A line graph is a series of points that are joined by straight lines.
They are usually used to show trends, which tell you how data changes over a period of time.
When you draw a line graph, make sure that:
r you put time on the horizontal axis
r you use an appropriate scale on the vertical axis
r you plot each point accurately
r you join the points with straight lines
r you give the line graph a title and label the axes.

Worked example 18.3

The table shows the value of a car over a
Age of car (years) 0 1 2 3 4
period of five years.
a Draw a line graph to show the data. Value of car ($) 25 000 20 000 17 000 14 900 13 400
b During which year did the car lose the
most value?
c Describe the trend in the value of the car.
1
d Use the graph to estimate the value of the car after 2 years.
2

a Age of car (years) goes on the horizontal
30 000 Value of car over five years axis.
Value of car ($) goes on the vertical axis.
25 000 The vertical axis has a sensible scale that
is easy to read.
20 000 All the points are plotted accurately and
Value of car ($) 15 000 labelled.
are joined with straight lines.
The graph has a title and the axes are

10 000

5000

0
1 2 3 4
Age of car (years)

b During the first year. The greatest loss is $5000 in the first year.
c The car goes down in value every year, but the The losses are $5000, $3000, $2000 and $1500 so
loss each year is less than the year before. each year’s loss is not as bad as the year before.
1
d $16 000 (see red line on graph) Read up from 2 on the horizontal axis to the
2
line, then across to the vertical axis to read off
the value.

184 18 Interpreting and discussing results