Exponential Growth and Decay Exponential growth and decay problems follow the model given by the equation A t Pert The model is a function of time t A t is the amount we have after time t P is the initial amount because for t 0 notice how A 0 Pe t Pe P r is the growth or decay rate It is positive for growth and negative for decay Growth and decay problems can deal with money interest compounded continuously bacteria growth radioactive decay population growth etc So A t can represent any of these depending on the problem Practice The growth of a certain bacteria population can be modeled by the function A t 350e0 0796 where A t is the number of bacteria and t represents the time in minutes a What is the initial number of bacteria 6 How long will it take for the number of bacteria to double round to the nearest whole number of bacteria b What is the number of bacteria after 20 minutes round to the nearest whole number of bacteria your answer must be acc