The population of a city (in millions) at time t (in years) is P (t) = 2.2e^ (0.006t), where t=0 is the year 2000. When will the population double from its size at t=0?

In 2000 population = 2.2 e (0.006*0) = 2.2 millions

when its doubled this = 4.4 so we have

4.4 = 2.2e^ (0.006t)

e^ (0.006t) = 2

0.006t = ln 2

t = ln 2 / 0.006 = 116

population will double in year 2116