# What is the formula to calculate population growth/rate?

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How do I use the formula for this word problem:

A small country that had 20 million people in 1990 has experienced exponential growth in population of 4% per year since then. Write an equation that models this situation and use your equation to determine when the population will double.

I know my formula ends up being:

P(n) = 20 x (1.04)^n

How do I use the formula for this word problem:

A small country that had 20 million people in 1990 has experienced exponential growth in population of 4% per year since then. Write an equation that models this situation and use your equation to determine when the population will double.

I know my formula ends up being:

P(n) = 20 x (1.04)^n

##### 1 Answer

#### Answer:

P(n)=P(0)*e^(k*t)

#### Explanation:

If P(n)=2*P(0) (n years later population will be double of the initial one).

Then

t= years

k=population growth rate per year (which is 0.04)

Note that there is no limiting factor (or carrying capacity) in this situation.

Compute

Again I underline there is no upper limiting factor. Population growth is exponential.