Step by step
The question
Question: 300 rabbits double each year.
Write the model.
1 Find the start
t is the time in years.
We call the number N.
At the start no time has passed: t = 0.
Then the number is 300.
That is the start.
2 Find the factor
To double means two times as much: times 2.
So the factor is 2: each year, we multiply by 2.
3 Make a small table
A small table: t = 0, 1, 2.
Each step, we multiply by 2: 300 times 2 is 600.
Times 2 again is 1200.
After 2 years, we multiplied by 2 two times.
Two times is the power 2: 2 squared.
After t years, we multiply t times.
So the power is t.
4 Write the model
Start times the factor, to the power t.
So the model is N = 300 times 2 to the power t.
5 Check
Let's check one more step, t = 3.
2 to the power 3 is 8.
300 times 8 is 2400.
One more step of the table: 1200 times 2 is 2400 too.
It works!
Let's look back.
First: find the start.
Then: find the factor.
Then: make a small table.
Then: write the model.
Last: check.