A new car is purchased for 22400 dollars. The value of the car depreciates at 11% per year. To the nearest tenth of a year, how long will it be until the value of the car is 5000 dollars?
100% - 11% = 89% of the value of the car retained after 1 year
5,000 =22,400 x 0.89^n
0.89^n =5,000 / 22,400
n = log(5,000/22,400) / log(0.89)
n = 12.87 years = ~12.9 years.