this problem is throwing me off. I've tried it for the past hour and can't get anywhere.

Given the formula for population N(t) at any time,

N(t)=C2 t/d (superscript) , where C is population at t=0
t is the time period elapsed
d is the doubleing period of the population

The population of the United States doubles approx. every 100 years. In 1980 the population of the U.S was 200 million. Find the projected population for the year 2180.

I don't know if this information is actually accurate to real life, but it would be neat to see the real solution.

2. Hello, dcfi6052!

Actually, they made the problem too easy!

Given the formula for population N(t) at any time: .$\displaystyle N(t) \:=\:C2^{\frac{t}{d}}$
where: $\displaystyle C$ is population at $\displaystyle t=0$
. . . . $\displaystyle t$ is the time period elapsed
. . . . $\displaystyle d$ is the doubling period of the population.

The population of the United States doubles approx. every 100 years.
In 1980 the population of the U.S was 200 million.
Find the projected population for the year 2180.

In 1980, the population was 200 million.
We are told that the population doubles every 100 years.

By the year 2180 (200 years later), it has doubled twice.

Therefore, the projected population for 2180 is: .$\displaystyle 2 \times 2 \times 20\text{ million} \:=\:80\text{ million}$