Now-Next and Population Models

1. Now-Next and Population Models Please view this tutorial and answer the follow-up questions on loose leaf to turn in to your teacher.

2. Example In 2000, India had a population of about 1.1 billion people. At that time, India’s net growth rate (or net change due to births and deaths) was 2.1% per year. Find India’s population in 2001. Write a Now-Next equation to model India’s population. The first thing we need to do is find the important information in the problem.

3. Example In 2000, India had a population of about 1.1 billion people. At the time India’s net growth rate was 2.1% per year. Find India’s population in 2001. Write a now-next equation to model India’s population. 1.1 billion people. What is our starting population? In 2000, the starting population was 1.1 billion people.

4. Example In 2000, India had a population of about 1.1 billion people. At the time India’s net growth rate was 2.1% per year. Find India’s population in 2001. Write a now-next equation to model India’s population. net growth rate was 2.1% How is the population changing from year to year? The population will increase by 2.1% each year.

5. Example Important Info: India 2000 population: 1.1 billion Net Change: 2.1% Now that we have our important information, we can find the population in 2001. First we need to find the net change due to births and deaths. Net change = .021*1.1 = .0231

6. Example Important Info: India 2000 population: 1.1 billion Net Change: 2.1% Now that we have our important information, we can find the population in 2001. Next, we need to add this net change to the original population. New population = 1.1 + .0231

7. Example Important Info: India 2000 population: 1.1 billion Net Change: 2.1% Now that we have our important information, we can find the population in 2001. Next, we need to add this net change to the original population. New population = 1.10231 billion

8. Example Important Info: India 2000 population: 1.1 billion Net Change: 2.1% Let’s combine the two steps. New population = 1.1 + .021 1.1 *

9. Example Important Info: India 2000 population: 1.1 billion Net Change: 2.1% Now we can replace the things that are changing in the problem with the words NOW and NEXT. New population = 1.1 + .021 1.1 *

10. Example Important Info: India 2000 population: 1.1 billion Net Change: 2.1% NEXT will replace the new population (or the value we are solving for). New population = Next = 1.1 + .021 1.1 *

11. Example Important Info: India 2000 population: 1.1 billion Net Change: 2.1% We will replace our initial population with the word NOW. Next = Now 1.1 + .021 Now 1.1 *

12. Example Important Info: India 2000 population: 1.1 billion Net Change: 2.1% You’ll also need to include your starting value, or Now-Start. Next = Now + .021 Now * Now-Start = 1.1 billion

13. Making Tables Once you have your equation, you can easily make tables. Next = Now + .021*Now N.S. = 1.1 billion Type in your initial population then hit ENTER.

14. Making Tables Once you have your equation, you can easily make tables. Next = Now + .021*Now N.S. = 1.1 billion Then enter your Now-Next equation by replacing Now with Ans (2nd Negative Sign) then hit ENTER.

15. Follow-Up Questions Answer the following questions on loose leaf and hand them in to your teacher.

16. Follow-Up Questions The population of Egypt in 2009 is 77.6 million. The growth rate is 1.68%. Find the population of Egypt in 2010 and 2011. Write a Now-Next equation to model the population of Egypt. When will the population reach 100 million?