Answer:
A = P x r^t
Explanation:
A = Amount (e.g. number of organisms in population after certain period of time)
P = Principal/ Initial Value (e.g. the starting population)
r = rate as a decimal (e.g. if a population increases over certain period of time by 20%, r would equal 1.2)
t = time in whichever units you need.
Example of problem using formula:
A population of 2000 decreases by 20% every year, find the population size after 5 years.
A = ?
P = 2000
r = 0.8
t = 5
A = Pxr^t
A = 2000 x 0.8^5
A = 655.36
Hope this helped!