According to the two censuses, the population of a country in 1980 was 4 million and in 1992 it was 9 million. assuming the population grows at the same rate(exponentially), what is the population of the country in 1995?
First we must find the rate at which it is increasing.
$\displaystyle P(t) = P(0)e^{kt}$
$\displaystyle P(0) = 4 000 000$
$\displaystyle P(12) = 9 000 000 = 4 000 000 \ e^{12t}$
$\displaystyle t = \frac{\ln \left( \frac{9}{4} \right)}{12} = 0,0675$
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And then simply plug it in.
$\displaystyle P(15) = 4 000 000 \ e^{15 \times 0,0675} = 11 022 704 \ approx.$