Data
t = time
N = sqare of feet infected
t=0 N=4
t=1 N= 3(4) =12
If every hour the sqare infected grow 3 times the previus hour it means that if we calculate the data for some hours it will be like this:




You can notice that the form growth occurs is:

where:
N is the sqare of feet infected
n is the numbner of the data related with the hours
Nn-1 is the square of feet infected is the las hour
If we put this in a graph it will be:
Seeing the graphic we can conclude that it is an exponential growing