The independent variable i<span>n exponential growth and decay problems is the time because the value of the given population will depend on the how much time have elapsed from the star of the decay or growth. in the usual form of a growth function is A(t) = Ao(e)^(kt)</span>
18% of 20000 = 3600(0.18 x 20000 = 3600) 3600 x 4 years = 14400 (original value - depreciated value in 4 years: 20000 - 14400 = 5600) The current value of the car is at £5600