Question: The population of United States was about 250 million in 2003, and was growing exponentially at a rate of about 0.7% per year. At this rate, what would be the population of United States in the year 2013?
A ) 233 million B ) 252.2 million C ) 268.1 million D ) 257 million
Steps to derive
1 From the data, the time t is 10 years, since it calculated from the year 2003 to year 2013.
2 The percent increase, r = 0.7% = 0.007.
3 The initial population, C = 250 million.
4y = C(1 + r)t [Write exponential growth model.]
5 = 250(1 + 0.007)10 [Substitute C = 250, r = 0.007 and t = 10.]
6 = 250(1.007)10 = 268.1 [Simplify.]
7 The population in the year 2013 would be 268.1 million.
