The amount of pollutant measured in parts per million, in Pine Lake can be modeled by the function: A(t) = 14e^-0.16t, where "t" is the number of years since a program to clean up the lake began. Approximately how long will it take for the amount of pollutant in Pine Lake to reach 7 million parts per million?

Solution:

14e^-0.16t = 7

So

t = 4.33

So it takes 4.33 years to reach 7 million parts per million