The average rate of change of the number of digital cameras can be found by dividing the change in the units by change in years.
B
b
The average rate of change of the number of film cameras can be found by dividing the change in the units by change in years.
C
c
In which sales is there an increase and in which one is there a decrease?
A
a
about 11 000 per year
B
b
about -5000 per year
C
c
See solution.
Practice makes perfect
a
We are given a graph that shows the number of digital still cameras and film cameras sold by Yellow Camera Stores in recent years.
The average rate of change r can be found using the following formula.
r=change in y/change in x = y_2- y_1/x_2- x_1
In the formula, y represents the number of cameras and x represents the years. Notice that there were 20 thousand digital cameras sold in 2004 and 75 thousand sold in 2009. Let's substitute the values into the formula and find the average rate of change.
The average rate of change of the number of digital cameras is about 11 000 per year.
b
We will find the average rate of change of the number of film cameras as in Part A. This time, there were 60 thousand digital cameras sold in 2004 and 35 thousand sold in 2009. Let's substitute the values into the formula and find the average rate of change.
Thus, the average rate of change for the number of film cameras is about -5000 per year.
c
The positive rate in Part A represents an increase in sales of digital cameras. The negative rate in Part B represents a decrease in sales of film cameras.
