The formula for exponential growth is:

y = a(1 + b)^{x}

where

y = the final amount

a = the original amount

b = the percentage change as a decimal, so 1 + b is the growth factor

x = time

**Example**

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?

**Answer**

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.