The formula for exponential growth is:
y = a(1 + b)x
y = the final amount
a = the original amount
b = the percentage change as a decimal, so 1 + b is the growth factor
x = time
The rabbit population in a farmer's field increases by 20% each year. There are currently about 50 rabbits in the field. If the farmer does nothing about the rabbits, how many will there be in 4 years?
a = 50
b = 20% = 0.20 = 0.2
x = 4
y = a(1 + b)x = 50 (1.2)4 = 103.68
There will be roughly 104 rabbits.