The U.S. population was 170 million in 1950 and 240 million in 1990. Assuming exponential population growth, what will the population be in the year 2020 Round your answer to the nearest million.
Select the correct answer.

A)250 million
B) 243 million
C) 486 million
D) 972 million
E) 311 million

Question

The U.S. population was 170 million in 1950 and 240 million in 1990. Assuming exponential population growth, what will the population be in the year 2020  Round your answer to the nearest million.  
Select the correct answer.
 
A)250 million
B) 243 million
C) 486 million
D) 972 million
E) 311 million

Quizplus · Accepted Answer

The exponential growth formula is $P = P_0e^{rt}$, where $P_0$ is the initial population, $r$ is the rate of growth, and $t$ is the time in years. Given $P_0 = 170$ million in 1950 and $P = 240$ million in 1990, we can solve for $r$ since $t = 40$ years. Then, using $r$ and $P_0 = 240$ million, we predict the population for 2020, which is 30 years from 1990. The calculation yields approximately 311 million.

The US Population Was 170 Million in 1950 and 240 Million