The graph shows that in 2000, there were 2.1 million pay phones. For the period from 2000 through 2006, this decreased by about .18 million pay phones per year.

Question

If this trend continues, when will there be no pay phones in the United States? Round to the nearest year.

Answer 1

If we visualize the graph, assuming that 2000 was used as year 0, that the y intercept of the graph is at 2.1 million, because in 2000 (year 0), there were 2.1 million pay phones. For the slope, we know that from 2000 to 2006, the amount of pay phones decreased by .18 million per year. So now we can come up with the equation:

 

y = -(1.8 million)x + (2.1 million)

 

We want to know at which year there will be 0 pay phones, so we must set y equal to 0, and solve for x:

 

0 = -(1.8 million)x + (2.1 million)

-(2.1 million) = -(1.8 million)x

11.667 = x

 

So it will take 11.667 years for there to be no pay phones, or, rounding to the nearest year, 2012.