Name:
Population Math
No calculators, show all work!
Growth Rate – Use this when you have actual population numbers (not rates)
Growth Rate = Current Population – Previous Population
Previous Population
X 100
To get an annual growth rate, divide the number you get above by the time
frame.
Example: In 1980, the population in Lane County was
250,000. This grew to 280,000 in 1990. What is the
annual percentage growth rate for Lane County?
Practice
1. A population of 1,000 has 30 births, 20 deaths, 15 individuals leave the
population and 20 come into the population. What is the growth rate?
2. A population of field mice was estimated to be 450. Over the course of a year
the following data was recorded: 800 births and 675 deaths. 25 new mice were
introduced into the population and 15 were removed. What is the growth rate?
3. The population in Highlands Ranch, CO was 70,000 in 2000. The current
population is 94,000. What is the annual growth rate of Highlands Ranch?
Growth Rate – Use this when you have rates for birth, death, immigration & emigration
Growth Rate = Birth rate – death rate + (immigration rate – emigration rate)
10
Practice:
4. A population has a birth rate of 3% and a death rate of 2%. Immigration was .5%
and emigration was 1%. What is the growth rate?
5. A population has a birth rate of 1.5% and a death rate of 2.25%. Immigration
was 1% and emigration was 1.5%. What is the growth rate?
Doubling Time
Definition:
Formula:
70/Growth Rate
Practice:
6. According the the CIA Factbook, United Arab Emirates and Burundi had the
world’s highest population growth rates at 3.69%. What is the annual doubling
time for these countries?
7. According to the CIA Factbook, Falkland islands and Norfolk Island both have the
lowest positive growth rates at .01%. What is the annual doubling time for these
countries?
8. A population of sea otters had a growth rate of 7% and a death rate of 3%. No
individuals left or entered the population. What is the annual doubling time of this
population?
Rate of Natural Increase
Definition:
Formula: r = b – d where r is rate of natural increase, b is birth rate and d is death rate
Practice:
9. A population of 1,000 has 30 births, 20 deaths, 15 individuals leave the
population and 20 come into the population. What is the rate of natural
increase?
10. How does your answer compare with your answer for #1?
11. What is the difference between the rate of natural increase and the growth rate?
12. When would you use the rate of natural increase instead of the growth rate?