In Example 1, we used two data points and an exponential function to model the population of the United States from 1970 through 2010. The data are shown again in the table. Use all five data points to solve Exercises 66–70.

Data from example 1

The graph in Figure 4.22 shows the U.S. population, in millions, for five selected years from 1970 through 2010. In 1970, the U.S. population was 203.3 million. By 2010, it had grown to 308.7 million.

Figure 4.22

Use the values of r in Exercises 66–69 to select the two models  of best fit. Use each of these models to predict by which year  the U.S. population will reach 335 million. How do these  answers compare to the year we found in Example 1, namely  2020? If you obtained different years, how do you account for  this difference?

x, Number of Years after 1969 1 (1970) 11 (1980) 21 (1990) 31 (2000) 41 (2010) y, U.S. Population (millions) 203.3 226.5 248.7 281.4 308.7