One way to model exponential growth and decay is with percentages Doing so we can use the following equation where a is the starting value r and its sign is the growth decay rate as a decimal and t is the time A a 1 r Note that the time and percent need to have the same respective units of time a Vehicles are known to depreciate at a rate of approximately 16 per year Write a model for the depreciation of a brand new 35 000 vehicle over time b In what year will your vehicle be worth 10 000