In Miami, the number of highway accidents increased by 20% over a four year period. How many accidents were there in 2013 if there were 5,120 in 2009?

We can model this scenario by using the exponential growth formula and plugging in values we know:

[tex]A = P(1+r)^{t}[/tex]

A, the resulting amount, is unknown
P, the principle (starting) amount, is 5120
r, the rate at which P increases, is .05 (if a .2 increase spans over 4 years, there is a .05 increase each year)
t, the amount of time that has passed, is 4

The equation now looks like this:

[tex]A = 5120(1.05)^{4}[/tex]

To find A, we just need to simplify the other side:

[tex]A = 6223.392[/tex]

In 2013, there were ~6224 Miami highway accidents (I rounded up because the amount was more than 6223, and you can't have a fraction of a car accident).