Exponential growth and decay by percentage

Lessons

1. exponential growth/decay by percentage
   
   The population of rabbits is increasing by 70% every 6 months.
   Presently there are 500 rabits. How many years will it take for
   the population to reach 1,000,000?
   
2. exponential growth/decay by percentage
   
   The intensity of light is reduced by 2% for each meter that a diver
   descends below the surface of the water. At what depth is the intensity of
   light only 10% of that at the surface?