As cell phones proliferate the number of pay phones continue

As cell phones proliferate, the number of pay phones continues to drop. The number of pay phones from 2004 through 2009 (in millions) are shown in the following table (x = 0 corresponds to 2004):

a. Plot the number of pay phones (y) versus the year (x).

b. Draw the straight line L through the points (0,1.30) and (5, 0.56)

c. Derive an equation for the line L

d. Assuming that the trend contines, estimate the number of pay phones in 2012.

Solution

The straight line L through the points (0,1.30) and (5, 0.56) IS GIVEN BY

(y-y₁)/(x-x₁) =(y₂-y₁)/(x₂-x₁)

That is (y-1.3)/(x-0) =(0.56-1.3)/(5-0)

(y-1.3)/(x)= -0.74/5

5y +0.74x=6.5 is the equation of the straight line

5y = 6.5-0.74x

Number of pay phones in 2012 is when x=8 here

5y = 6.5-0.74*8 = 6.5-5.92=0.58

y=0.116