SOLUTION: This one's killing me... In 1980, there were about 168 million vehicles and about 233 million people in the United States. The number of vehicles has been growing at 4% a year,

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Question 154514: This one's killing me...
In 1980, there were about 168 million vehicles and about 233 million people in the United States. The number of vehicles has been growing at 4% a year, while the population has been growing at 1% a year.
(a) Write a formula for the number of vehicles as a function of years since 1980.
I came up with V(t)=168(1.4)^t; which seems to work out via calculator, but is incorrect.
I would greatly appreciate any help!!

Answer by BrittanyM(80) About Me  (Show Source):
You can put this solution on YOUR website!
I think I might have found a solution for you.

I'm not sure if you're familiar with PERT, Pe%5Ert but it's a very useful model for computing population growth over time. In this case, we can use it to model the growth of motor vehicles over time.

So for this little problem, I came up with

V(t) = 168%28million%29e%5E%280.04t%29

We set this up by knowing that in Pe%5Ert, P is the principle (or the population where time is zero), r is rate, and t is time.

If you choose values for time and plug this into your calculator, you shouold come up with pretty accurate answers.