A country's current population is 100 million with an annual growth rate of 3.5%. If the growth rate remains constant, what will be the population in 40 years?

Since the population growth rate is 3.5 annual that implies that the increase in population has to be recalculated at the end of each year (i.e. it is not a constant amount like a 100 people or a 1000 people but it changes every year)

To solve this problem we will use the following equation

[tex]P_{t} = P_{0} (1 + r)^t[/tex]

Where

[tex]P_{n}[/tex] is population at year 't'

[tex]P_{0}[/tex] is initial population i.e. 100 million

[tex]r[/tex] is growth rate is a fraction i.e. 3.5/100

[tex]t[/tex] is years passed i.e. 40

Now all we have to do is plugin the values

[tex]P_{40} = 100000000 (1 + \frac{3.5}{100} )^4^0[/tex]

The answer is 395,925,972