In 1990 the population of the U.S. was approximately 250 million and was expected to grow according to the function
P(x) = 250,000,000e 0.009x, where x is the number of years after 1990. When will there be three times as many people in the U.S. as in 1990, according to this model?

Question

In 1990 the population of the U.S. was approximately 250 million and was expected to grow according to the function 
P(x) = 250,000,000e 0.009x, where x is the number of years after 1990. When will there be three times as many people in the U.S. as in 1990, according to this model?

stormfire1 · Answer

$$750,000,000=250,000,000*e^{0.009x}$$
$$3 = e^{.009x}$$
$$\ln 3 = 0.009x$$
x = ~122 years