# CCGPS CA 3.3.2 Example 2

In 2008, about 66 million U.S. households had both landline phones and cell phones. This number decreased by an average of 5 million households per year. Use the table below to calculate the rate of change for the interval [2008, 2011].

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1. Determine the interval to be observed.
2. Determine $(x_1, y_1)$.
3. Determine $(x_2, y_2)$.
4. Substitute $(x_1, y_1$) and $(x_2, y_2)$ into the slope formula to calculate the rate of change.

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