Question

The population of the world in 1987 was 5 billion and the annual growth rate was estimated at 2 percent per year. Assuming that the world population follows an exponential growth model, find the projected world population in 2015. 3 significant digits in the final answer.

Answer 1

The projected world population in 2015 is 8.71 billion

Here, we want to use an exponential model to find the world's population in the given year

Generally, we can have the exponential model as;

`P=I(1+r)^t`

where P represents the population in the year 2015

I represents the population in 1987

r is the annual growth percentage = 2% = 2/100 = 0.02

t is the difference in the number of years = 2015-1987 = 28

Substituting these values, we have;

`\begin{gathered} P=5,000,000,000(1+0.02)^(28) \\ \\ P=5,000,000,000(1.02)^(28) \\ \\ P\text{ = 8,705,121,030.86965} \end{gathered}`

Which to 3 significant digits is 8.71 billion