When interpreting graphs, take a good look at the graph before your start.

Be sure you look for the following:
  • Does the graph have a title? (such as "Books Sold", or "Distance Traveled"?)
     Titles usually appear on graphs that represent real-world situations.
     They give you a quick impression of what the graph will be about.

• How are the axes labeled? (such as time, distance, number of items, etc.)
     Look at labels on both the horizontal and the vertical axes.
• What units are used to label the axes? (is distance in inches, feet, miles etc?)
     Be careful! Questions about the graph may be using a different unit label. (i.e. yards)
• What scale is used on each axes? (1 tick mark = 1 mile or 1 tick = 10 miles)
     Take particular notice if the scales are different on the two axes.
• What is the shape of the graph? (a line, a curve, parts of a line, dots?)
     Most of our graphs will be straight lines, but not all of them.

bullet Reading a Basic Math-Style Graph:
basicgraph This is a basic math-style graph. It deals with a coordinate grid, a line, and a scale. There is no indication that this represents a real-world situation.

Look carefully at the scale.
(1 unit per tick mark on both axes)

Look at where the line crosses the y-axis.  b = (0,3)

Look carefully at the slope of the line.   m = -3/2
(rise over run)

The equation of the line:    bequation

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bullet Reading a Graph that Models a Situation:


treadmill

Description given for the graph:
Erin has set her treadmill
to a speed that will allow her
to walk 2 miles in 30 minutes.

Common types of questions asked:
a) What is the slope shown on this graph?
     miles3
b) What does the slope represent?
    The rate at which she is walking: 1mile per 15 min.
    or 115th of a mile per minute.

c) Write an equation representing the miles traveled, y, in terms of the minutes walked, x.
     miles2
d) If Erin wishes to walk one mile, how long must she remain on the treadmill?      15 minutes
(reading from y-axis to x-axis)

e) If Erin remains on the treadmill for 20 minutes, how far will she have walked?
(reading from x-axis to y-axis)
    miles1

 

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