Exponential Growth Decay Word Problems 6 You have inherited land that was purchased for 30 000 in 1960 The value of the land increased by approximately 5 per year What is the approximate value of the land in the year 2011 7 During normal breathing about 12 of the air in the lungs is replaced after one breath Write an exponential decay model for the amount of the original air left in the lungs if the initial amount of air in the lungs is 500 mL How much of the original air is present after 240 breaths 8 An adult takes 400 mg of ibuprofen Each hour the amount of ibuprofen in the person s system decreases by about 29 How much ibuprofen is left after 6 hours 9 You deposit 1600 in a bank account Find the balance after 3 years for each of the following situations a The account pays 2 5 annual interest compounded monthly b The account pays 1 7 5 annual interest compounded quarterly c The account pays 4 annual interest compounded yearly