Qm q8.) use the model to determine when the population of the country will be 855 million.

A graphing calculator finds the value of t to be about 17 for A = 855 million.

The population of the country will be 855 million in 2020.

Comment
There are a couple of ways you can do this. I think the easiest way is to use logs. Use the Natural log key on your calculator. Just looking at the equation tells you that the population will increase. You know that because the constant the e is raised to is greater than zero.  The population would decrease if k<0 See below for what I am calling k.

Givens
A = 855 million or just 855
C = current population = 619.2 in millions
k = 0.019
t = ???

Formula
A = C*e^(k*t)

Substitute and Solve
855 = 619.2 * e ^(0.019)*t Divide both sides by 619.2 
855/619.2 = e^0.019*t
1.3808 = e^0.019 * t  Take the natural log of both sides.
ln(1.3808) = ln( e^0.019t)
ln(1.3809) = 0.019t ln e    But the ln (e) = 1
ln(1.3809) = 0.019t  take the natural log on the left
0.32267 = 0.019 * t  Divide by 0.019 on both sides.
0.32267/0.019 = t
t = 16.9828  Which rounded = 17 years.

Conclusion
The starting population was determined in 2003. !7 years later, the ending population would be reached. 

Answer 2020 the ending population would be reached <<<<