Answer: 4.3 years
Step-by-step explanation:
Given: The population of a species of starfish in the Gulf of Mexico is decreasing at an exponential rate
To find the population we have given an equation
, where k is the decay rate (k<0) in t years and
is the initial population.
Five years ago the population was 10,000, in 2015 it is only 2000.
So put t=5 ,
and A(t)= 2000 in the above function we get

Taking log on both sides, we get

Taking 2015 as the initial year
, To find t when A(t)=500

Taking log on both sides, we get

Hence, This event will occur in 4.3 years from 2015.