A.4.17.3 Phones in Homes

In 2004, less than 5% of the homes in the U.S. relied only on a cell phone. Since then, the percentage of homes that used only cell phones have increased. Here are the percentages of homes with only cell phones from 2004 to 2009. 1. Suppose a linear function, P, gives us the percentage of homes with only cell phones as a function of years since 2004, t. Fit a line on the scatter plot to represent this function and write an equation that could define the function. Use function notation.

2. Use your equation to find the value of P(6). Then, explain what it means in this situation. 3. Use your equation to solve P(t)=30 for t. What does the solution represent? 4. Suppose we want to know when the percentage of homes with only cell phones would reach 50%, 75%, or 100% (assuming that the trend continues and the function stays valid). What equation could be written to help us find those percentages? Show your reasoning.